954 RECORD OF CURRENT RESEARCHES RELATING TO 



animal life are confined to the anterior portion of tlie body, while the 

 hinder part contains the generative organs. But, nevertheless, it is 

 only gradually that the head takes on the higher sensory functions 

 and becomes sterile. At first it is the head which is the largest part 

 of the body ; in the trunk, differentiation commences in the anterior 

 portion, and growth is terminal. This is the typical mode of growth 

 which leads in time to the typical metameric animal. 



Excretory Organs in the Trematoda and Cestoida.* — M. Frai- 

 pont has a fuller paper on this subject,! which is illustrated by two 

 plates. 



In dealing with the morphology of the excretory system in 

 the Vermes, he points out that, on a comparative examination, there 

 are two types of renal organs. In the Turbellaria, Nemertinea, 

 Cestoida, Trematoda, and Eotifera, there is a system of canals, with 

 walls, which are probably glandular, and which ojien into the coelom 

 by a number of ciliated infuudibnla, and are connected with the outer 

 world by a single and median, or by two lateral vesicles. On the 

 other hand, in the Anuulata (Hirudinea, Oligochfeta, Chfetopoda) there 

 are true segmental organs (uephridia — Laukester) which are always 

 multiple and paired. In the Gephyrea both sets of organs appear to 

 be present. 



Coming to closer details, it is possible to detect in the Trema- 

 toda : — 



(1) A terminal vesicle, posterior in position ; or two vesicles, 

 ventral and anterior. 



(2) Into this there open by two trunks a system of large canals. 



(3) These canals communicate with lymphatic spaces by ciliated 

 infundibula. 



(4) From these, canaliculi pass into the larger canals. 

 Practically similar arrangements are to be seen in the Cestoida ; 



but it is to be noted that in some, at any rate, of the forms which 

 exhibit a segmentation there are a number of pores communicating 

 with the exterior ; and this is of interest as pointing to the mode by 

 which in the Annulata a number of organs may have become deve- 

 loped. 



In the Dendrocoelous Turbellarians, Hallez has denied the presence 

 of an excretory apparatus, but the observations of Schmidt, Schultze, 

 and Kennel would appear to make its presence almost certain. Not- 

 withstanding contradictory statements, an arrangement is also to be 

 found in the Nemertinea (especially Malacohdella) which is exactly 

 formed on the same type as in the Ehabdocoela. 



In the Rotifera we again find an organ formed of three constituent 

 parts : (1) a terminal vesicle, single or double, and ordinarily placed 

 at the hinder end of the body, (2) two large lateral trunks, with a 

 glandular wall, and (3) small canaliculi which open into the general 

 cavity of the body by one or more ciliated infundibula. This general 

 concordance in structure is in striking agreement with the well- 

 known views of Professor Gegenbaur. 



* ' Arcli. de Biol.,' i. (1880) p. 415. + See this Journal, ante, p. 802. 



