54 pnocKEDiNflS or the 



large quarto illustrated volume. The memoirs already issued are 

 such as to render it a duty for every well-wisher of zoological 

 science to become a subscriber. 



Platthelmia. — Passing on to the AVorms, we find that very 

 important work has been done during the past year, on the one 

 hand by Dr. Arnold Lang of the Zoological Station, and on the 

 other hand by M. Frai])ont of Liege. Dr. Lang has made known 

 for the first time with aitythiug like accuracy the form of the 

 nervous system in the Planarire, the Trematoda, and the Cestoidea. 

 Speaking generally, we may say that Dr. Lang's observations 

 are confirmatory of those of Dr. Ilubrecht on the Nemer- 

 tines. Dr. Ilubrecht discovered a complete nerve-tunic in the 

 latter group of worms in which certain longitudinal cords are dif- 

 ferentiated. Dr. Lang finds, similarly, much as recent researches 

 have made known for the Medusa>, a com2)lete subepidemic nerve- 

 plexus in the three groups of flat worms studied by him : within 

 this nerve-plexus longitudinal trunks (as many as eight) may be 

 differentiated. The study o£ a remarkable segmented Planarian 

 worm, Gwida segmentata, has convinced Dr. Lang of the close 

 affinity of the Platyhelmia to the Leeches on the one hand, and 

 to the Ctenophora on the other. The comparison with the latter 

 group has been carried out in detail by Dr. Lang ; and he is led 

 to the conclusion that the alimentary canal with its ramifications 

 is identical in the two cases, and that the excretory canal-system 

 of the flat worms is but a special development of this system. 

 When the identification by Hackel o£ the parts of a Ctenophore, 

 such as Pleurolracliia, with those of a craspedote Medusa is borne 

 in mind, the immense importance of the conclusions to which Dr. 

 Lang's researches tend becomes apparent. For a proper appre- 

 ciation of his views we must refer to his original papers in the 

 ' Mittheilungcn ' of the Zoological Station of Naples. Scarcely 

 less interesting have been Fraipont's discoveries with regard 

 to the termination of the fine ramifications of the excretory or 

 ncphridial canal-system of Planarian, Cestoids, and Trematodes, in 

 the form of minute funnels leading into an excessively fine net- 

 work of intercellular spaces, which must be regarded as a canali- 

 cular or spongiform body- cavity ('Archives de Biologie'). The 

 exact limits of the nephridia of these worms are thus determined, 

 as lately established by Biitschli for Cercaria ; and it is apparent 

 that in structure and relation to the general organization of the 

 animal they arc identical with the excretory organs or nephridia 

 ol" the Eotifera. 



MoLLUscA. — Not less important, and really following on the 

 same lines, are the researches which have this year been pub- 

 lished on the most worm-like of the Mollusca, viz. the Chitons 

 and the vermiform Neomenia, Proncomenia, and Cha>toderma. 

 It is plain, from Hubrecht's account of these animals, which form 

 the group of Amphineura ((^uart. Journ. Micr. Sci., April 1882), 

 that the nervous system, consisting essentially of two or of four 



