210 



INTERNAL FACTORS 



IV. i 



EucJiaris by shaking. These gave rise to half larvae, provided 

 with four costae, four meridional canals communicating with two 

 subsagittal an:l two subtransverse canals in the ordinary way, 

 one subgastric canal, one tentacle, but a whole funnel and a whole 

 stomach, the latter formed by an oblique invagination ; the side 

 turned towards the missing blastomere was covered over by ectoderm. 

 Later on the missing half was regenerated, first the subgastric 

 vessel, then the meridional canals s over these the costae, and 

 finally a tentacle. 



FIG. 119. Development of isolated blastoiueres iu Ctenophora. a, 6. 

 Segmentation of \ blastomere of Berne orata : a, two large, two small 

 cells ; b, each gives off a micromere ; c Larva from a \ blastomere with 

 four costae ; c7, e. Segmentation of \ blastomere ; /. The resulting larva 

 with two costae ; g. Larva with six costae from f blastomeres. (After 

 Driesch and Morgan, 1896.) h. Isolated -f s blastomeres of Beroe orata ; 

 j. The resulting larva with four costae. one sense-organ, and one 

 stomodaeum ; i. Isolated ^blastomeres; k. The resulting larva with three 

 costae, one sense-organ, and one stomodaeum. (After Fischel, 1898.) 



Such half larvae are found in the tow-net after a storm and 

 may become (Bolina) sexually mature. 



These experiments have been repeated arid confirmed on Beroe 

 by Driesch and Morgan. The authors add that the segmentation of 

 these isolated blastomeres is partial. The larva has two costae 

 only and a large and a small canal, the former passing to the 

 costae, the latter to the opposite side and representing apparently 



