ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 795 



parasitic alternating with a dioecious and free life — as Wtabdoncma, 

 and Angiostomum, are now placed in the separate suborder of the 

 Bhabditifornife, and the family Rhabdonomidaa. 



Excretory and nervous system of Duthiersia and Solenophorus.* 

 — M. J. Poirier describes the excretory system of D. expansa and 

 S. megaloccphalus as consisting of two pairs of longitudinal vessels 

 connected by a transverse vessel in each ring. The external vessels 

 are more delicate than, and placed dorsally to, the internal vessels ; 

 tho walls are not cellular, but are formed of a thickening of the 

 connective tissue that surrounds tbem, and of a muscular coat. In 

 the head the internal vessels are merely represented by a network 

 of vessels; at some distance from the bead a series of secondary 

 vessels is met with ; starting from this region the principal vessels 

 give off a large number of branches. Some ramify a great deal and 

 are especially numerous in the central region of the rings, where they 

 terminate in funnels ; others pass peripherally and unite to form a 

 lacunar vessel, placed inside the nervous system. 



The nervous system in the rings consists of two large longitudinal 

 cords placed outside the excretory system. These pass into tho 

 head and pass along the wall of the sucker; at the anterior 

 extremity each forms a ganglion, which are joined together by a 

 transverse commissure. In Duthiersia the nerves in the head give off 

 lateral nerves, and from each ganglion a couple of nerves 'are given off, 

 each pair of nerves uniting to form a ring. The other lateral nerves 

 form a network, which lies close below the sucker. In Solenophorus, 

 tho nerves in the head give off no lateral branches, and each of tho 

 lateral nerves from the two ganglia has itself a ganglion upon it ; the 

 two nerves unite to form a ring as before ; this nerve-ring lies just 

 below the muscular ring of the sucker. The difference exhibited 

 by the nervous system in these two genera is probably connected 

 with the different mode of fixation to the host found in each. In 

 Duthiersia the villi of the intestine are compressed by tho whole surface 

 of the sucker, whereas in Solenophorus the villi are clasped only by 

 the muscular rim of the sucker. 



Parasites of Malapterurus.j — Prof. G. Fritsck describes various 

 helminth-parasites from this electric fish. Corallobothrium is a new 

 genus of Cestoda, which appears to bo intermediate between the 

 Bothriocephalidee and the Tfeniidre. It has a terminal cavity in which 

 there are four suckers arranged crosswise ; no neck ; and typical 

 gonads with marginal orifices. The form of the head is very liko 

 that of Caryophyllseus. The sole species known is called C. solidum. 

 There is also a new Taenia which is called T. malapteruri. Of the 

 Nematoids, Trichosomum papillosum sp. n. was found in the stomach, 

 and even in young examples of the fish there were specimens of 

 Filar ia piscium, which were cncapsuled in the body-cavity, in the 

 muscles, and even in the electric organ itself. The author justly 



* Comptcs Bendus, cii. (188G) pp. 700-3. 



t SB K Preuss. Akad. Berlin, 188(5, pp. 90-108 (1 pi.). 



