EMBRYOLOGY. 1 



Morphology of the Vertebrate Urino-genital System.— 

 From a detailed study of the excretory and reproductive organs of 

 Ichthyophis glutinosus, one of the Cajcilians, Professor Semou, of Jena, 

 is led to a conception of the vertebi system contain- 



ing many joints of interest and importance. 



The material used consisted of embryos, larva? and adults obtained 

 in Ceylon by P. and F. Sarasin, and is fully described in the first sixty 

 pages of text with the aid of fourteen plates. 



Passing on to the comparative discussion of the results obtained, 

 illustrated by diagrams, we may first give the chief facts observed by 

 the author and then some of his applications of these to the morph- 

 ology of the excretory and reproductive organs in the entire vertebrate 

 groups. 



The pronephros consists of at least twelve pairs of tubes, one pair in 

 each segment, opening into two pronephric ducts that run to the 

 cloaca and opening at the other end by fun nels into the body cavity. 

 The dorsal part of the body cavity receiving tiiese twelve pairs of tun- 

 nels is constricted off as a tube on each side, remaining, however, still 

 in communication with the large ventral part of the coelom by slender 

 tubes that become secondary funnels. These tubes next app«M ■* 

 branches of the original pronephric tubules, each of which now has 

 two funnels, a ventral and a dorsal one. The dorsal tube of coelom is 

 then partly divided by ingrowths of vascular loops, gL 

 chambers, one for each dorsal funnel. These chambers are tin Mat- 

 pighian bodies of the pronephros. Irregularities appear in the branch- 

 ing and connections of the pronephric tubules both anteriorly and In- 

 teriorly in this long series; finally secondary changes occur and the 

 organ loses its function. Before this takes place the mesonephros 

 appears and both function at the same time. Though chiefly posterior 

 to the pronephros the mesonephros also extends forward so that both 

 organs occur in the same segment. Then it is seen that the mesone- 

 phros is dorsal to the pronephros. At the very first the mesonophnc 

 tubules are strictly segmental, but very soon the secondary, tertii** 

 etc., tubules destroy the metameric arrangement. Each tubule has a 

 funnel opening into the large coelom and also opens by what m*J 

 regarded as a second funnel into the Malpighian capsule. These meso- 



