71)6 SUMMARY OF CURRENT RESEARCHES RELATING TO 



remarks on the extraordinary character of the last-named site, where 

 the parasites must ho exposed to the full force of the electric shock. 



Studies on Rhabdoccel Turbellarians.* — In his first contribution 

 Dr. L. Bohmig deals with the genus Graffilla, first described by v. 

 Ihering in LS76. After some account of the external form tho 

 author describes his methods of study. Tho worms were treated 

 with hot and cold solutions of corrosive sublimate, 1/2-2 per cent, 

 solutions of chromic acid, Kleinenberg's picric acid solution, and 1 per 

 cent, osmic acid. Tho first gave the best results. For museum 

 purposes they arc best killed with picric acid. 



The author gives a detailed account of the organs, even of parts 

 that have been already correctly described by previous observers. 



Histology of Acoelous Rhabdocoela.t — M. Y. Dclage finds, from a 

 study of Convoluta schultzii, that the investment of the body is formed 

 by a layer of ciliated cells, which have partly lost their individuality, 

 and of the three most muscular layers. Within tho body there are, 

 in addition to the reproductive organs, a well-developed otocyst, two 

 eye-spots, a frontal organ which has the function of tactile sensation, 

 and is, possibly, also olfactory, a well-developed nervous system, and 

 germ-cells. The whole of the free space is occupied by the reticulum, 

 which is dense in the head, rarer in the superficial layers of the body, 

 and still rarer in tho central parts. It is, however, everywhere con- 

 tinuous, and there is no distinct digestive cavity. The nerves are in- 

 vested in an endothelial sheath, formed of connective-tissue cells, 

 which completely separate them from the other organs. With regard 

 to the lacunae in the reticulum the author desires to speak with some 

 reserve. He believes that in Convoluta, at any rate, this reticulum 

 represents a true connective tissue, and that it is not a continuous 

 mass, hollowed out by vacuoles. He points out that all the space cir- 

 cumscribed by the integuments, and invaded by the reticulum, which 

 occupies without filling it, represents the fused general and digestive 

 cavities. If this be so, the reticulum is merely an unimportant sup- 

 porting tissue, arranged so as to consolidate the organism, without 

 forming any complete septa. Everything is found in a common 

 cavity and bathed by common fluids. If, on the other hand, the 

 reticulum forms a continuous and closed system, it establishes some 

 kind of order. The lacunar are closed, the food and the zoochlorella3 

 are separate from the nerves and the sexual products, and have their 

 special modes of exit. 



With regard to the small cells which Mr. Geddes has called Pul- 

 satella Convolutse, M. Del age states that they are caliciform, have no 

 nucleus, and have their cavity occupied by a tuft of cilia which move 

 rhythmically. This cavity does not appear to communicate with 

 special ducts, or with the lacunar of the reticulum. In favour of the 

 view of Geddes that they are protozoic parasites, it is to be noted that 

 they are not regularly distinguished through one animal, or equally 

 through several. One Convoluta may have thirty or forty, and another 



* Zeitschr. f. Wiss. Zool., xliii. (1886) pp. 290-328 (2 pis.), 

 t Arch. Zool. Expc'r. et Gen., iv. (18SG) pp. 109-60 (2 pis.). 



