104 THE EVOLUTION OF CONTINUITY 



type evolved the highest Segmental organisms, or Verte- 

 brates. For the present we shall only observe that the 

 strobila of Aurelia must " represent " the development in 

 compressed lateral Continuity of a very large number of 

 ancestral sporosacs in series. Thus, we might imagine a 

 " spray " of eight sporosacs compressed as one medusiform 

 gonophore, and a "spray" of sixty -four as going to make 

 a succession of eight such organisms. 



At the present day there are Hydrozoa which produce 

 gonoblastidia containing not sporosacs but medusiform 

 gonophores, which arise from the sides of the central stem ; 



¥ia. 35. — Explaining the evolution of strobilar continuity. 

 A, B, showing how four (potential) laterally produced sporo- 

 sac-gonoblastidia could by developing under compression 

 take form as a gonoblastidium containing four medusiform 

 gonophores (see Figs. 29, A, B, c) ; c, a long sporosac- 

 bearing stem whose development under compressing influ- 

 ence could result in a straight series of medusiform gono- 

 phores, as pictured in D ; E, the more complete compression 

 of these in strobilar continuity. 



and our belief is that each gonophore here represents the 

 compression of a laterally produced sporosac-gonoblastidium 

 (Fig. 35, A, B). But in the case of the primitive Aurelia 

 we are drawn to conclude that the strobila would represent 

 the development in compression of one long unbranching 

 stem capable of bearing very many sporosacs, which in 

 successive multiples would form successive medusoids 

 (Fig. 35, C, D, E). It is needless to say that the compression 

 would be applied to the series all through its development. 

 All the development of the present-day Aurelia is clearly 

 megazooidal, and the Individual should in time be repre- 



