602 THE FORMS OF TISSUES [ch. 



which may have existed, and given rise to the appearance which the 

 observer drew. These drawings may be compared with the diagrams 

 on p. 598, in which the twelve possible arrangements of five inter- 

 mediate partitions for a system of eight cells have been set forth. 



It will be seen that Robert-Tornow's figure of the segmenting egg 

 of Trochus (Fig. 248) clearly shews the cells grouped after the fashion 

 of l\ while Conkhn's figure of the ascidian egg (Cynthia) shews 

 equally clearly the arrangement e. A sea-urchin egg segmenting 



Fig. 251. Egg of Pyrosoma. 

 After KorotneflF. 



Fig. 252. Egg of Echinus, segmenting 

 under pressure. After Driesch. 



Fig. 253. (a) Part of segmenting egg of Cephalopod (after Watase) ; 

 (6) probable actual arrangement. 



under pressure, as figured by Driesch, scarcely wants any modifica- 

 tion of the drawing to appear in one case as type /, in another as g. 

 Turning to a botanical illustration, we have a figure of Pringsheim's 

 shewing an eight-celled stage in the apex of the young cone of 

 Salvinia: it is ill drawn, but may be referable, as in my diagram, 

 to type /; after it is figured a very different object, a segmenting 

 egg of the ascidian Pyrosoma, after Korotneif, also, but still more 

 doubtfully, referred to /. In the cuttlefish egg there is again some 

 uncertainty, but it is probably referable to g. Lastly, I have 

 copied from Roux a curious figure of the frog's egg, viewed from 

 the animal pole; it is obviously inaccurate, but may perhaps 

 belong to type e. Of type i, in which the five partitions form 



