304 



DISCOVERY REPORTS 



an extreme form of this chitinoid development (Fig. 25 d, e). Despite the great dif- 

 ference between forms such as those shown in Figs. 25 a, b and 25 d, e, there is every 

 reason to suppose that the one may develop from the other and that they are conspecific. 

 Further, it is almost certain that the tangential skeleton of styli, the irregularity of the 

 tornota, etc., are correlated with the development of the chitinoid ectosome and may 



Fig. 25 . a-e, Tedania massa, Ridley and Dendy, showing some of the variations in external form ; /, Tedania 

 tenuicapitata, Ridley, showing similarity of form due to the growth of an encrusting Haliclona around the 

 basal half. 



possibly be induced by it. What gives rise to this ectosome is, however, still a mystery ; 

 but it is interesting to note that in some of the more typical individuals of T. massa 

 irregularly rounded patches of such an ectosome occasionally occur and that their 

 presence is always accompanied by some derangement of the outer layers of the skeleton, 

 although a tangential layer of styli may not have been formed. This cuticle is so con- 



