426 ZOOLOGY. 



The group has been again investigated — tliis time by Prof. E. Metschni- 

 Koff — with the following results : 



The Orthonectids may be said to be forms which, on the whole, develop 

 a radiate plan of structure, and have a ciliated and segmented dermal 

 layer, well-developed generative organs, and well-marked dimorphism of 

 the sexes. Professor Metschnikoii" considers them to be probably degen- 

 erated forms, and suggests that they may be most nearly related to the 

 Turbellariaus, through Dinophilus, a member of the latter group, which 

 has also a sui)erficial ciliary segmentation and well-marked sexual 

 dimorphism. The sexes are developed from diversiform eggs, the males 

 arising from the smaller eggs and the females from the larger. The 

 males are minute, and their "only evident organ is a spacious testicular 

 sac." The representatives of the "class" move in a straight course, 

 and consequently negative the suggestion of Eabl-Euckhard, that the 

 radiate plan of structure is due to movement within a restricted area. 

 (J. E. M. S., (2,) I, pp. 461-462, from Z. W. Z., XXXY, pp. 282-304, 1 pi.) 



PLATYHELMINTHES. 



]. General. 



Lang (A.). Uutersuchungen zui- vergleicheuden Anatomie uud Histologie des Nerven- 

 Bystems der Plathelminthen. Mittheil. Zool. Station Neapel, v. 3, pp. 53-96. 



. Der Ban von Gnnda segmentata nnd die Verwandtscliaft der Plathelmin- 



then mit Coeleuteraten und Hirudineen. Ibid., v. 3, pp. 187-25L 



2. Special orders. 



Cestoda. 



Stein(S. Th.). EntwickelnngsgescliichteundParasitismusdermensclilichen Cestoden. 

 Mit 79 Illnstrat. and 115 micropliotogr. Abbild. auf 14 Taf. nach J. Grimm. 

 Labr, Schauenbnrg, 1881. (8vo. M. 18.) 



Trematoda. 



Fraipont (J.). Organes excrdteurs des Tr^matodea et Cestodes. Bull. Soc. Beige. Mi- 



croscop., t. 7, 1881, pp. xxxi-xlii. (Abstr.: Journ. Boy. Microscop. Soc, {2,) v. 1, 



pp. 741-742. 

 Pagen8teclier(H. Alex.). ZnrEntwickelungsgescliichtederTrematoden, insbesoudere 



liber Arbeit des Prof. Giambatt. Ercolani : Dell' Adattamento, etc. Verliandl. nat.- 



med. Ver. Heidelierg, n. F., v. 3, pp. 33-56. 



Tiirbellaria. 



Silliman (W. A.). Sur un nouveau type de Turbellari6s. Compt. rend. Ac. Sc. Paris, 



t. 93, pp. 1087-1089. 

 Seleuka (Emil). Zoologiscbe Studien. II. Zur Eutwickelungsgescbiclite der See- 



plauarien. Eiu Beitrag zur Keimbliitterlehre und Descendenztbeorie. Mit 7 Taf. 



nnd 2 Holzschn. Leipzig, Engelmann, 1881. (4to. v, 44 pp. M. 6.) 



A new suborder of Turhellarians. 



Parasitic on a Nematoid worm — itself parasitic on the Echinoderm, 

 UcMnns sphwra — occurs a peculiar form, which has been investigated 

 by Mr. W. A. Silliman. The animal is of sublanceolate form, about 



