322 MR. M. r. WOODWARD ON THE [Mar. 28, 



examination of these under a high power showed them to consist 

 of a large amount of lightly staining protoplasm, with an enormous 

 central nucleus, whose chromatin was aggregated into one immense 

 nucleolus, staining darkly, while the nucleus itself remained prac- 

 tically unstained. 



The general structure of these cells at once suggested ova, and on 

 a careful comparison with the normal ovum (Plate XXIV. fig. 5 a, b), 

 it will be seen that it is impossible to distinguish the large cells of 

 this accessory gland from ripe ova and the few moderate-sized 

 cells from developing ones \ 



Thus we have in this specimen situated on the 11/12 mesentery, 

 just above the coiled portion of the vas deferens, on the right side 

 a body indistinguishable from a testis, and on the left side one 

 consisting of a ground-mass of testicular tissue, in which are 

 imbedded a few undoubted ova. In other words, we have here on 

 the left side a true hermaphrodite gland, comparable in all its 

 essentials to the ova-testis of a hermaphrodite mollusk, and, like 

 that, budding-off sperm mothei'-cells into the coelom, the ova 

 remaining adherent to the wall of the gland until fully formed. 



In most hermaphrodite invertebrates known the male and 

 female genital glands are quite distinct from one another ; in fact 

 it is only in some MoUusca and a few Crustacea where we find 

 genuine hermaphrodite glands. Bernard has described such a 

 condition in ^jjms ",where spermatozoa were developed in the ovary ; 

 and Ishikawa ^ has discovered the constant presence of ova in the 

 posterior part of the testis of Gehia. We have now recorded this 

 condition in a third group of Invertebrata, viz. the Chsetopoda. 



Leaving on one side the question as to a probably hermaphro- 

 ditism of the ancestral worms, we may safely regard the ova and 

 sperm mother-cells, the ovaries and the testes as a whole, as being 

 homologous structures among the Oligochaeta, for we have seen 

 that ovaries or testes may either develop iudiiSerently upon 

 mesentery 11/12 or be replaced by a true hermaphrodite gland. 



I have already pointed out (I.e. p. 187) that ovaries may occasion- 

 ally be developed on the mesenteries 11-18, and now I have only 

 to record the fact that the presence of additional ovaries is much 

 more frequent than has been supposed, especially on mesentery 

 13/14 (figs. 1 and 6, ov') and not unfrequently on 11/12. 



A very curious condition in the development of an ovary is 

 seen in the specimen under notice, where a mass of ova, mature and 

 immature, was found in a special cavity surrounded by a thin epi- 

 theloid capsule, to which the eggs were attached, immediately under 



^ There seemed just a possibility that these large cells might be encysted 

 Gregarines, and, in order to settle this question, sections were made of the ovary 

 of an Earthworm which had a number of these parasites encysted within it. 

 The difference between these cells and the parasites was at once manifest — the 

 coarsely granular protoplasm and large nucleus with its curiously vacuolated 

 nucleolus ol' the parasite contrasting strongly with the almost homogeneous 

 protoplasm and compact intensely-staining nucleolus of the ovum. 



» ' Nature,' vol. xliii. p. 343. 



= Zool. Anz. xiv. 1891, p. 70, 



