ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 323 



only connected more or less closely with one another when they possess 

 strongly branched dendrites which form networks. There are four types 

 of motor-cell. 



Platyhelminthes. 



Orientation of the Cestoda.* — Ludwig Cohn makes some striking 

 suggestions on this subject. He holds that the key to the morpho- 

 logical significance of the Cestode body is to be found in the oncosphere. 

 Its front end is the hook-bearing end, which in movement is directed 

 anteriorly. In all taded Cysticercoids the embryonal booklets of the 

 oncosphere are found on the caudal appendage, which is thus to be 

 regarded as the anterior end of the Cysticercoid. There is a stage in all 

 Cestodes when the whole anterior body is lost, and in the proliferating 

 scolices we have animals which without possessing a real anterior end, 

 i.e. a head, fix themselves by the hinder end to the gut wall, and hang 

 with their relatively most anterior end freely suspended in the gut. 

 This thesis thus assumes (1) that in Cestodes the anterior and the posterior 

 body arise separately from a middle piece ; (2) that the hinder part 

 detaches itself aud alone enters into the composition of the sexual animal ; 

 (3) that the zone of growth of Cestodes occurs not on the front end 

 close behind the head, but, on the contrary, away from it. These 

 points are fully discussed in the paper. 



Sterility in Cestodes.f — Al. Mrazek found an example of Tatria 

 acanthorhyneha which possessed only male organs and a receptaculum 

 seminis. Another individual possessed in the youngest (anterior) pro- 

 glottids distinct rudiments of single parts of the sex-organs, e.g. cirrus 

 sac, etc., but in the oldest proglottids had not the slightest trace of these 

 organs or their rudiments. It is regarded as probable that the develop- 

 ment had proceeded so far and stopped, and that the rudiments then 

 disappeared. It is possible that these phenomena have some relation to 

 the rare cases of Cestoda in which the sexes occur separate. 



Hemiuridse.l — A. Looss deals with the anatomy and classification of 

 the members of the Distomid family Hemiuridas, giving a detailed 

 account of its sub-families, genera, and species. The members of this 

 family are inhabitants of the alimentary canal of marine bony fishes. 

 They are entirely or nearly cylindrical, and in some, though not in all, 

 the body consists of two regions, trunk and abdomen (Schwanzanhang). 

 The skin is always unarmed, and the suckers, which are muscular and 

 powerful, are set close together. The eggs are extremely numerous, 

 thin-shelled, and relatively small, usually about " 02 mm., exceptionally 

 ' 03 mm. in length. 



*&' 



Rhythmic Behaviour of Convoluta Roscoffensis.§— Louis Martin 

 has made some new and interesting observations on this subject. He 

 finds that darkness inhibits the movements, which synchronise with the 

 tides. Convoluta does not rise in darkness, or if it have done so, it 



* Zool. Anzeig., xxxii. (1907) pp. 51-66. 



+ Centralbl. Bakt. Parasitenk., xlv. (1907) p. 234-5. 



X Zool. Jahrb., xxvi. (1907) pp. 63-180 (9 pis.). 



§ Comptes Rendus, cxlv. (1907) pp. 555-7. 



