410 



WILLIAM J. DAKIN 



discovery has very considerably modified the views of the 

 function and meaning of the infra-cerel)ral vesicles. 



If any definite theory of the function of these structures 

 can be said to be generally accepted, it is that they represent 

 the ectoderm from which the nervous system arose in the 

 embryo, and in a recent paper by Duboscq the suggestion is 

 made that the infra -cerebral vesicles remain, even in the adult 

 stage, structures for the renovation or increase in size of the 

 supra-oesophageal ganglia. Cells are supposed to be cut off 

 from the vesicle colls and to migrate into the ganglia, there 

 to become either new nerve-cells or supporting cells. 



Text-fig. 1. 



vo 



Peripatoides occiden talis: section of so-called ventral 

 organ, vo ; c, cuticle ; E, ectoderm ; M, muscles of body-wall ; 

 s, strand connecting ventral organ with lateral nerve-cord. 



The present note has been written because in several of 

 our best preparations from the head of Peripatoides 

 occidentalis, Dendy, of Western Australia (5), the histology 

 of the organs in question is not the same as that illustrated by 

 Duboscq (6). And a little more may be said in explanation of 

 the presence of these curiously definite structures. 



According to Duboscq (who examined Opisthopatus 

 cinctipes, Purcell) one can distinguish in these organs two 

 distinct regions, (a) the vesicle, (b) the ganglion intermediare. 

 The latter is the part which former writers have called the stalk 

 or peduncle of the vesicle. The term ' ganglion intermediare ' 

 is unsuital^le, especially since it appears that Duboscq himself 



