340 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Vermes. 



Peculiar mode of Copulation in Marine Dendroccela.* — Claparede 

 has already shown that in the genus Thjsanozoon there are two penes 

 and two male genital orifices, but only one orifice in the female. This 

 observation has not only been confirmed by A. Lang, but much ex- 

 tended ; he having found at Naples forms with nine or even fifteen penes. 

 It is obvious that these could hardly have been intended to be intro- 

 duced into the single vagina. The true signification of the contrivance 

 was elucidated by the observation of the copulatory process in several 

 species of Proceros — the penis was thrust indiscriminately into the 

 body of the female, and through the wound thus formed the semen 

 flowed into the oviduct which is distributed throughout the body. 

 The female organ therefore serves only as an exit for the eggs. 



Classification of the Nematohelminthes.t — Dr. L. Orley pro- 

 poses to establish three suborders, to which he would give the names 

 of Nematentozoa, Ehabditiformae, and Anguillulidse ; the last are 

 fitted for a free life, and are characterized therefore by the presence of 

 circumoral bristles, lateral circular markings, and a caudal sucker ; 

 the Khabditiformfe are intermediate, for, while they lack the charac- 

 ters just mentioned, they resemble the free-living and dififer from the 

 parasitic Nematentozoa in having a thin cuticle, and a single straight 

 tube, as well as in the fact that their nervous system is either entirely 

 absent, or consists only of a few fibres. So, again, while all Nematoids 

 have free larvae, those of the parasitic group perish unless they enter a 

 host ; the Anguillulidse do not so enter, but develope in mould or water, 

 while the Ehabditidse may or may not enter into hosts. There is an 

 arrangement of the genera,- with short diagnoses, and two new species 

 of Filaria, F. spiralis and F. ecaiidata, are described. 



Relations of the Platyhelminthes.J — Dr. A. Lang gives an 

 account of the results to which he has been chiefly led by his 

 study of Gunda segmentata.% Considering first of all the Polyclades 

 as creeping Ctenophores, he points out that, in his opinion, the 

 Coeloplana of Kowalevsky is not intermediate between the Ctenophora 

 and Planaria, but is a true creeping Ctenophore ; this form is remark- 

 able for being flattened, for having the ctenophoral plates absent, and 

 for a complete investment of cilia. The fact that external conditions 

 can produce such great changes prevents us from giving any importance 

 to such characters as these, when we compare the two groups. To 

 most of the internal points of resemblance between them attention 

 has already been directed ; but with regard to the development, we 

 may note that Selenka has lately pointed out the striking similarity 

 he has found in the earlier stages; and the observations of Lang 

 are confirmatory of the fact that the embryo of the Polyclades 

 is at first radial, and that it is only later that it becomes bilaterally 

 symmetrical. 



* Arch. Sci. Phys. et Nat., vi. (1881) p. 308. 

 t Ann. and Mag. Nat. Hist., ix. (1882) pp. 301-18. 

 J Arch, fie Biol., ii. pp. 533-52. 

 § fScu this Juiu'iuil, auk, p. 197. 



