490 



As a result of this growth of the testes away from the ovary, the 

 testes are attached to the body wall more or less separately from the ovary. 

 This condition has frequently been described as 'testes separated from 

 the ovaries'. This expression would lead to the idea that the two were 

 independent. The position of the vas deferens on the ovary shows that 

 they are not independent but that they belong to the one gonad. Han- 

 cock in 1867 and Lacaz e-D uthiers and Delage in 1892 maintai- 

 ned that in Styela variabilis the numerous testes opened separately into 

 the atrial cavity and were independent of the ovary. This was doubt- 

 less an error. The vasa efferentia and vas deferens are seen only with 

 great difficulty unless filled with spermatozoa. I have not been able to 

 examine Styela variabilis, but in the nearly related 8. partita the ducts 

 have the customary relation to the ovary. 



Fig. VI. 1. Part of a gonad of Pelonaia corrugata (X 16); 2. a gonad of Katatropa 



vancouverensis (X 12). 



This group contains species which are in many respects the most 

 highly organized of Styelids. The peculiar stalked forms of the North 

 Pacific (one has recently been described from the Cape of Good Hope 

 by Dr. Hartmeyer and I understand that Dr. Michaelsen has re- 

 ceived one from the coast of West-Africa) all belong to this group. The 

 peculiar spinules of the siphons reach their highest development in this 

 group. 



The testes in this group show considerable variation in their method 

 of growth. The species may be divided into two distinct groups on a 

 basis of the way in which the testes react to the body wall. Loeb has 

 given the name stereotropismto that condition in which an organism 

 tends to place itself close against the substratum. Organisms growing 

 against the substratum are positively stereotropic and those growing 

 away from the substratum are negatively stereotropic. In one group 



