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XXL.—On the Anatomy of Ocnerodrilus (Eisen)

Published online by Cambridge University Press:  17 January 2013

Frank E. Beddard
Frank E. Beddard
Affiliation:
Prosector of the Zoological Society of London, Lecturer on Biology at Guy's Hospital.
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Extract

The worms which form the subject of the present communication were forwarded to me, in a living condition, from Kew Gardens.

I have received lately a considerable number of living Oligochæta from those Gardens, through the kindness of Mr Dyer, who permitted me to have the earth arriving from different parts of the world in the Wardian cases, in which plants are packed for travelling, thoroughly sifted, with a view to preserving the worms which had been accidentally included. By these means I have succeeded in obtaining some very interesting new forms, as well as a number of others which are still imperfectly known. The species which I describe in the present paper appears to be a new species of Eisen's genus Ocnerodrilus. The genus Ocnerodrilus was formed by Eisen in 1878 [1] for a small worm found in Fresno County, California. The specimens were all met with in “an irrigation box,” where they were found crawling among the algæ which covered the boards. It is evidently, therefore, aquatic in its habits, but Eisen contrasts its slow movements with the rapid swimming of Lumbriculus and Rhynchelmis, comparing it in general appearance with a small species of Lumbricus.

Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 36 , Issue 2 , 1892 , pp. 563 - 583
Copyright
Copyright © Royal Society of Edinburgh 1892

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References

page 563 note * I desire also to record my appreciation of the careful way in which Mr Crisp, one of the employés at Kew, has sorted out and transmitted to me these and other specimens.

page 565 note * With regard to the Luinbriculidæ, the number of segments occupied by the clitellum has not yet been accurately described in many types. In Rhynchelmis, Vejdovsky [15] implies that the clitellum occupies segments VIII–XVI.

page 567 note * In Acanthodrilus antarcticus and in the young of A. multiporus. I do not know how far this ciliation is prevalent among Earthworms.

page 573 note * In these Oligochæta there is hardly any distinction between a glandular and non-glandular section of the atrium.

page 574 note * I assume that the structures which have been usually termed “prostates” in the Earthworm correspond to the atria of the aquatic genera. This question has been lately revived by Benham, who is not of my opinion [10].

Before pointing out the reasons which lead me to adhere to my own view, I would say a few words concerning an apparent confusion in my description which is pointed out by Benham. He says: “Beddard takes up rather a curious position in regard to the prostate of Moniligaster. For him, the peritoneal coat, outside the muscular wall of the atrium, is the ‘prostate,’ and is homologous with the ‘Cementdrüse’ (or prostate) of Tubifex. Now this prostate in Tubifex has been shown by Vejdovsky to be formed by a proliferation and outgrowth of the atrial epithelium at a certain point, which bursts through the muscular wall of the atrium and projects into the body cavity. The atrial epithelium is derived from the epidermis, so that the ‘Cementdrüse’ is epiblastic, whereas the glandular covering of the ‘atrium’ of Moniligaster, Stylaria, Rhynchelmis, &c., is mesoblastic,—if it is in reality a modification of peritoneal cells. Hence Beddard would regard the epiblastic ‘prostate’ (Cementdrüse) of Tubifex as the homologue of the mesoblastic covering of the atrium of Moniligaster !!”

In my own Memoir, to which Benham refers [23], I compare (on p. 120) the glandular investment of the atrium of Moniligaster with a corresponding investment of the atrium in Rhynchelmis, which I write down as “prostate,” indicating by the inverted commas that I follow the nomenclature of Vejdovsky. Further on I again (on p. 126) make use of the term prostate in describing this glandular investment, but have omitted the inverted commas, which renders my terminology a little confusing. I do not, however, in that paper compare the glandular investment of the atrium in Moniligaster and Rhynchelmis with the Cementdrüsen of Tubifex.

In a preliminary notice of these facts, however [22], I did make this comparison, which appeared to me to be to some extent justified by the remarkable fact that the Cementdrüsen of Tubifex are not covered by a peritoneal coating. I came to the conclusion later that the apparent discrepancy between Vejdovsky's statements and figures might be of less importance than I had thought it.

As to the terminal glandular structures attached to the vasa deferentia of Eudrilidæ, Perichætidae, Acanthodrilidæ, &c., it appears to me impossible to refer them to more than one category.

Mr Benham indicates very clearly (except in fig. 4) the different layers which constitute these organs in a number of types, but omits any representation of the family Eudrilidæ; it is precisely here that we meet with conditions which render it impossible to distinguish between “atrium” and “prostate.” Mr Benham allows “that a portion of the prostate of Perichæta, Eudrilus, and other genera in which the sperm duct and the prostate join, is probably the homologue of the ‘atrium’ of Tubifex.” To follow out this admission to its logical conclusion it is necessary to draw a distinction between the part immediately preceding and the part immediately succeeding the point of opening of the vasa deferentia; that is to say, we must regard as different two parts of a tube in the Eudrilidæ and in the Lumbriculidæ between which there is no trace of a break, and not the faintest difference in minute structure !!

page 576 note * I am inclined to think that Rosa's failure to find spermathecæ in Microscolex dubius may be due to the fact that they are only, as in Ocnerodrilus, present for a short period.

page 576 note † Vejdovsky's figures of Phreatothrix [15, pl. xi., figs. 18, 19] show the Xlth as the ovarian segment, but his table on p. 132 states the Xth segment.

page 578 note * We require, however, more information about Ilyodrilus, which resembles the Naidomorpha in certain points.

page 579 note * This scheme is practically identical with that proposed by D'Udekem in 1853 [13], and further elaborated in 1863 [14]. The division is into “Agemmes” and “Gemmipares” these names implying the principal distinction between the two groups. Another distinction referred to is the persistence of the genital organs in the “Agemmes” and their appearance only at certain epochs in the “Gemmipares.”