492 



remaining connected with it by a narrow stalk traversed by the vasa 

 efferentia (Fig. III). This process appears to be quite distinct from the 

 stereotropic reaction. In these genera the lobes of the testes (not the 

 masses) do not project into the atrial cavity but are closely bound tog- 

 ether. 



In the negatively stereotropic forms [Styela and Katatropa) we have 

 the reverse condition. In the early stages, before any lobes are formed, 

 the testes elongate perpendicularly to the body wall (Fig. IV, K. yaku- 

 tatensis). In K. greeleyi (Fig. IX, 4) little or no lobing occurs and the 

 testes of the adult are long cylindrical structures projecting freely into 



Fig. IX. 



Fig. X. 



Stye la 



Katatropa 



K. van- 



3 4 



Fig. IX. Testes of Styela and Katatropa viewed from the side. (X 10-) 1 



couverensis; 2, S. costatum; 3, S. partita; 4, K. greeleyi. 

 Fig. X. Diagrams to show the relative positions of the gonads in Styela and Kata- 

 tropa. The form of body shown is that of the stalked species. The testes are not 



indicated. 



the atrial cavity. In most species the testes become lobed and the lobes 

 diverge from each other and project freely into the cavity (Figs. VIII 

 and IX). The greatest extreme in branching is shown by S. partita 

 (Fig. IV and Fig. IX, 3). When the testes are very closely placed, the 

 branches may not be able to diverge and may be forced to grow together 

 more or less (Fig. VIII on the right side). Masses so formed may su- 

 perficially resemble the masses formed by the positively stereotropic 

 testes but close inspection will at once show the difference. 



The ovary shows certain differences throughout the series of forms 



