344 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



germs which was noted is now more distinctly manifested by the 

 presence of organisms at very various stages of development. To the 

 author's great astonishment he. found that the products of the 

 sporocyst were not Distomata, but Bedim ; these, when free, are about 

 0'4-0"7 mm. long, but are capable of considerable contraction and 

 extension ; a head, median region, and tail-end may be distinguished ; 

 the two former are separated sharply from one another by a prominent 

 encircling ridge, while the body is distinguished from the tail by two 

 blunt projecting processes, developed from the ventral surface. The 

 tail is bluntly conical. The lips surrounding the mouth serve as 

 attaching organs. The organization of the Media presents very con- 

 siderable resemblance to that of the embryos, the organs being only 

 more strongly individualized and the elementary parts more distinct, 

 in correspondence with the larger body and higher function. The 

 encircling ridge may be looked upon as a kind of skeletal girdle, 

 which serves as the point of attachment for the retractors of the head 

 and pharynx. As to the mode of development of this Bedia, the 

 author believes that it passes through a gastrula stage ; though some 

 points were made out, the history of the germ-spheres could not be 

 followed. Here then, unfortunately, this part of the history comes to 

 an end ; luckily some other snails were obtained in which were found 

 three Bedim ; two of these contained Cercari^, but a third had a tail- 

 less Distomum which is believed to have been a young D. hepaticum. 



In conclusion, some remarks are made on the small Lymnfeids 

 which are believed to be the hosts. 



Excretory Apparatus of Turbellaria.* — In continuing his 

 studies,! P. Fraucotte points out that Hallez denies the existence 

 of the excretory canals in the genus Monocoelis, while Schultze and 

 others distinctly affirm their existence. The author has been able 

 to confirm the latter doctrine, so far as it applies to the presence of 

 these canals, but he has not been able to detect any communications 

 with the outer world. On the other hand, he has discovered the pre- 

 sence of ciliated terminal infundibula, very similar to those of the 

 Trematoda and Cestoda. 



In dealing with the genus Monocoelis, it is, first of all, necessary 

 to take for examination perfectly fresh specimens ; there will then be 

 seen a system of principal canals, fine secondary canaliculi which 

 form a plexus throughout the whole, and vibratile infundibula united 

 to the plexus by a canal. There are two pairs of principal canals on 

 either side of the middle line, two external and two internal ; these 

 are united with one another by several anastomoses of the same size ; 

 the distinct walls are transparent and very hyaline, but no definite 

 histological structure could be made out. At certain points there 

 may be seen a long conical filiform cilium ; the canals contain a 

 transparent liquid in which are some small granulations. The secondary 

 canaliculi arise from the ciliated infundibula and have a very delicate 

 wall, of no distinct structure ; they are best made out in the anterior 



* Bull. Acad. R. Belg., iii. (1882) pp. 88-98. 

 t See this Journal, i. (18S1) p. 4H0. 



