898 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Entozoic Worms.* — Dr. v. Linstow's annual paper on this 

 subject gives descriptions of forms already known, at any rate by 

 name, as well as accounts of new species. Twenty-six species are, in 

 all, discussed, of whicb nine are new. There are some interesting 

 observations on the widely distributed Gordius aquaticus, in which 

 the author makes some criticisms on the account given by Villot. 



Nervous System of Trematodes.t — From the observations of E. 

 Gaffron it appears that in Distomum isostomum the nervous, system 

 consists of sis longitudinal trunks connected together by a com- 

 plicated system of commissures ; there are three limbs on either side, 

 one ventral, one dorsal, and one lateral. They unite anteriorly to 

 form a dorsal cerebral commissure, which lies above the anterior part 

 of the oesophagus. From the two lateral enlargements four nerve 

 cords are given off, two anteriorly and two posteriorly. The ventral 

 and dorsal longitudinal trunks undoubtedly correspond to the lateral 

 nerves of D. hepaficiim ; at the hinder end of the animal they converge 

 and pass into one another, while the lateral nerves remain separate. 

 Sis transverse bridges lying one behind the other, unite the ventral, 

 dorsal and lateral trunks, and give rise to a wide-meshed nervous 

 plesus in which are placed the viscera and generative organs. The 

 ventral sucker is innervated by strong branches given off from the 

 dorsal and ventral nerves. The minute structure of the nervous 

 system offers no deviation from that already described by Lang. 



Rhabdocoela from the Depths of the Lake of Geneva.j — - G. Du- 



plessis-Gouret, who attaches very great importance to the animals 

 discovered at great depths either in sea or fresh water, gives an 

 account of the Ehabdocoela of the Lake of Geneva ; of these about 

 a dozen species were found, of which one-fourth are new (? first found 

 in the Lake of Geneva). There is evidence of their afl&nity to very 

 ancient forms, and proofs that they are the remnants of a marine 

 fauna. 



The first worm mentioned is Macrostoma Jiystrix of CErsted ; the 

 second Microstoma lineare (Erst. ; this is remarkable for the complete 

 absence of rhabdites from its integument, and for their replacement 

 by what the author calls trichocysts ; these are not, however, com- 

 parable to the organs so named by AUman in Paramcecium, but to the 

 nematocysts, as they are ordinarily called, of Hydra ; the author 

 thinks that this discovery is of special importance in relation to the 

 views of Lang as to the affinities of the Turbellaria and Ctenophora. 

 Ciliated pits on the side of the head remind us of the similarly 

 named parts in the Nemertinea. There is no anus, which is 

 usually stated to be present in this genus ; the intestine is provided 

 with muscular walls and esecutes peristaltic movements — a pheno- 

 menon unknown in any other Ehabdocoele. The sexual organs are 

 of the simplest character, and the sexes are distinct. The ovary 



• Arch. f. Naturgesch., 1. (1884) pp. 125-45 (3 pis.). 



t Sclineider's Zool. Beitrage, 1884, pp. 109-14 (1 pi.). Of. Biol. Centralbl., 

 iv. (1884) pp. 425-6. 



% Arch. Zool. Exper. et. Gen., ii. (1884) pp. 37-68 (1 pi,). 



