ZOOLOGY. , 489 



As to the nervous system, "both developmentally and histologically, 

 the ventral cord agrees" with that of the annulates. Although the 

 peripheral system of the Gordiids is very differeut from that of the An- 

 nulata, " it is not difficult to find homologies between the two." Other re- 

 semblances are found by Dr. Vejdovsky in -'the structure of the body 

 wall, the hypodermis of the Euchytraeidae being exactly like that of the 

 Gordiidse; Polygordius, again, has, like Gordius (and the nematoids), 

 no circular muscular layer." Also the structure of the muscular tissue 

 is of the annulate and not of the nematoid types. The characteristics 

 of the Gordiids, thus briefly hinted at, are sufiQcient, Professor Vejdovsky 

 thinks, to entitle the Gordiids to be isolated as an independent order, 

 and for this the name of Nematomorpha is proposed. (Zeitschr. f. wiss. 

 Zool., XLiii, pp. 369-433, 2 pi. ; J. R. M. S. (2), vi, p. 988.) 



Myzostomids. 



The relations of the myeostomids. — The curious parasites of the crinoids 

 known as myzostomids. and having some superficial resemblance to 

 mites, have been examined as to their anatomy and histology by Mr. 

 F. Nansen. Various peculiarities of the nervous system have been 

 described as well as characteristic features of other parts, but for a 

 knowledge of these reference must be made to the original memoir or 

 to a full abstract in the Journal of the Royal Microscopic Society. It 

 will be sufiBcient here to summarize the results of the investigations 

 upon complemeutal males and the systematic position of the group. 



Complemental males were found in three »\)Q,cm^^ M. giganteum, M.gi- 

 gas, and M. carpenteri. Such males are "similar in structure to the her- 

 maphrodites, except that where the latter have ovaries, the males have 

 tubes with slightly developed cells, so that they have a certain resem- 

 blance to young ovaries ; the dorsal oviduct (uterus) is feebly, but the 

 lateral oviducts are well developed. The author disagrees with Beard 

 as to the secondary origin of the hermaphroditism of Myzostomida, in- 

 asmuch as the dioecious species are the most parasitic, and the rudi- 

 ments of testes in M. cysticolum appear to be rather remnants of an 

 androgynous stage than budding developments of male organs." 



The systematic relations of the group, according to our author, are 

 rather with the chaetopods, from which, nevertheless, they are suffi- 

 ciently distinct. They also show "a tendency towards certain arach- 

 nids fLinguatulida, Tardigrada, and perhaps Pycnogonida) and crusta- 

 ceans." On the whole, however, it is believed by Mr. Nansen that the 

 group is derived " from the Trochophora, and, among archiannelids, are 

 related to Histriodrilus." (Bidrag til Myzostomernes Anatomi og His- 

 tologi, Bergen, 1885 5 J. E. M. S. (2), Vi, pp. 019-621.) 



