| OCR Text |
Show 828 MR. F. E. BEDDARD ON [Nov. 6, shape of these glands may be understood from the same drawing. From transverse sections through the body, it could be seen that these glands are closely adjacent to the terminal portion of the vasa deferentia (Plate LII. fig. 9) just before they perforate the mesentery. . These glands possibly correspond to a pair of somewhat similar glands described and figured by Perrier in Pontodrilus l ; they are also possibly to be compared to two glandular masses which I have described myself in Megascolex*. The position of these glands exactly corresponds to that of the ovaries, attached as they are to the anterior mesentery of their segment close to the middle ventral bne ; their structure exactly resembles that of the ovaries in those regions where the fully formed ova are not found. A more positive proof that these glands are the morphological equivalents of ovaria is the fact that in one example of A. dissimilis, that I have studied, by means of transverse sections, the posterior right-hand gland contained abundant ova, which resembled in every detail the ova produced by the true ovaries which lie in the succeeding segment. Beyond this single fact, which maj7 be an abnormality, hut, like other abnormalities, serves as clue to a morphological comparison, I have no evidence to offer as to the function of these structures. The fact that there are frequently more than a single pair of testes in Earthworms-there are two pairs for example in the present species-renders it more probable still that the comparison which I have instituted is a correct one. The multiplication of ovaries, as well as of testes, naturally recalls the condition met with in hermaphrodite Polychseta. These species of Acanthodrilus appear, in fact, to have preserved more completely than any other Earthworms, the anatomy of which is known, the primitive condition of the generative organs. There is no Oligochsetous Annelid in which more than a single pair of ovaries are known with certainty to occur ; Euclipidrilus, according to Eisen", possesses three pairs of ovaries ; and in Chato-gaster limnai, Lankester3 has described two pairs which are not mature at the same time. Vejdovsky4, however, states that he has never succeeded in finding the second pair in Ch. limnai, and is of opinion that Eisen has mistaken other organs for the additional pairs of ovaries in Euclipidrilus. The above suggestion as to the homologies of these anterior glands is also borne out by their relations in the third of the three species, viz. A. multiporus. It has already been mentioned that the ovaries of this Acanthodrilus, instead of being attached to the anterior wall of the 13th segment, are attached to its po^erior wall in close connection with the oviduct. There is a similar change in position of the glandular bodies, which come to lie beneath the funnels of the 1 Loc. cit. pi. xiv. fig. 9, pi. xvii. fig. 37, and loc. cit. p. 504. 2 Roy. Soc. of Sciences, Upsala, 1881. 3 Quart. Journ. Micr. Sci. vol. ix. new ser. 1869. 4 System unci Morphologie der Oligochceten. Prag. 1884, p. 115. |
