198 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and that from the funnel there arise the gastro-vascular canals, in 

 the form of paired ones which pass off laterally and branch, and an 

 unpaired one which passes to the aboral pole, and there opens ; on 

 the other hand, the unpaired branch in Gunda only opens to the 

 exterior in an early stage. 



The Polyclades, like the Ctenophora, are hermaphrodite ; and in 

 buth groups the generative products arise in close relation to the 

 branches of the enteron ; Chun has described them as having, in 

 the Ctenophora, their origin in the ctenophoral vessels, that is to say, 

 from the endoderm ; in the Triclades they are developed from the 

 enteric epithelium, so that the homology would appear to be complete. 



The excretory organs of the Ctenophora are regarded as being 

 represented by those pores by means of which the branches of the 

 vessel of the funnel are brought into relation with the outer world ; 

 in Gunda it consists of large canals, which anastomose with one 

 another, and of a number of fine excretory capillaries which are 

 considerably branched, but which do not anastomose. The large 

 canals here and there give off large branches to the dorsal surface 

 of the body without opening into contractile vesicles. Throughout 

 the whole body of the animal there are scattered a number of 

 smaller or larger vacuoles, which have a considerable resemblance to 

 the contractile vesicles of the Infusoria. These vacuoles are not 

 arranged irregularly, but are united into small groups, and when one 

 of them is examined, we see that it is supplied by a branch from the 

 excretory capillaries, and there is a ciliated band between the 

 vacuoles. A fact, to which the author attaches much importance, is 

 the presence of a large number of ciliated infundibula in and on the 

 epithelium of the branches of the enteron. The vacuoles which 

 surround the funnel cannot be distinguished from those which are 

 found in the enteric cells ; the protoplasm of the ciliated funnel is 

 the plasma of an enteric cell, and the funnel is a hollowed endodermic 

 cell, ciliated within. The homology between these structures and 

 the protoplasmic networks to which they give rise, with the inter- 

 cellular lymphatic plexus of Fraipont and Francotte, and the sub- 

 cutaneous nerve-j)lexus found by Ihering in Graffilla muricola is 

 insisted on, and it is found that, taking all the characters into con- 

 sideration, they must be regarded as being formed on the same type 

 as those of the Coelenterata. 



The musculature of the Polyclades arises from the four primitive 

 cells of the mesenchyma ; the cells which are to become muscular 

 fibres are arranged in layers under the epithelium, and their arrange- 

 ment, like the mode of locomotion, is different to that which is seen 

 in the Coelenterata, but it is to be explained as due to their creeping 

 mode of life, which demands a more regular distribution of the fibres, 

 and a greater development of the superficial muscles. 



Our space will not allow us to follow the author into the com- 

 parisons which he institutes between Gunda and the fresh-water 

 Triclades, or the Hirudinea ; he finds, however, that the Leeches are 

 closely allied to Gunda ; and dealing with Trochosphcera, he points out 

 that all larvae of its type are only provided with organs which are, 



