Explanation of Fi,8;ures. 



Plate XXV. 



Fig. ]. — Egg with two Llastomeres. x4B (Zeiss). 



Fig. 2. — Egg with three (a) and lorn- hlastomeres {!>). x 4 1>. 



Fig. 3.- — Egg with eight hlastomeres, side view, x 4 B. 



Fjo'. 4. — Egg witli thirty two blastomere', seen from tlio future ventral 



side. X 4B. 

 Fjf. T), — Yoiino- morula, ventral view, x 2 D. 



Fig. G, — Ventral view of an advanced hlastula in which the gastral in- 

 vagination has become visible from the outside, x 2 D. 

 Fig. 7. — Ventral view of a gastrnla, in which the blastopore has tal^en a 



triangular form. x 2 D. 

 Fig. 8, — Side view of an advanced gastrula, in which the blastopore has 



become a transverse sHt. x 2 D. 

 Fig. 0. — Young ActiuotroclKt in whii-h tlui n(q)hridial \\\i is visible from 



the outside, x 2 D. 

 Fig. 10. — Larva of four tentacles (side view). x 2 D. 

 li'io-. 11. — ]\Ietamorphosiug larva of type A, sketched from a preserved 



specimen, x 4 A. 

 Fig. 12- — Larva of type D, sketched from a living specimen. Greatly 



magnified. 

 Fig. 13. — Larva (of 14 tentacles) of type A, in the living state. Greatly 



magnified. 

 Fig. IJ. — Highly advanced larva of type B, bearing 28 tentacles, ventral 



view. Greatly magnified. 

 Fi"'. 15. — Lnrva of type C, bearing 20 tentacles, n represents a dorsal 



view, b a ventral view, and c tlie multicellular gland on the hood. 



Greatly magnified. 

 Fig. IG. — Larva of type D, bearing 48 tentacles, after |)reservntion. Greatly 

 magnified. 



