LÉUCOPSACÙS ORTHODOCCS. 45 



come to intersect one another with their elonsiHted rnvs. After 

 reachino- a. certain size, each sino-le oxvstauractin is distinctly 

 outwardly convex, in conformity with the rounded external surface 

 of the larva. The convexity becomes more and more pronounced 

 as the spicule grows larger, which takes place with comparatively 

 greater rapidity than the growth of the larva in general size. 

 The entire skeleton, considered apart from the soft parts, represent 

 a hollow spherical basketwork composed of the loose oxystauractins. 

 (In figs. 24 and 25, PL III., the soft parts are drawn as seen 

 in optical sections, while the spicules put in are all those that 

 could be seen in one-half of the larva by focussing the microscope 

 up and down). 



In the stage shown in fig. 24, PL III., in which the 

 aj^proximately spherical body measures about 70/'- in diameter 

 and the spicules reach up to 30 !>■ or thereabout in axial length, 

 the soft parts still appear to retain the same histological character 

 as before the formation of s])icules. At places favorably situated 

 for the observation, there is to be seen on the surface a granular 

 coating, indicating the presence of flagella to the external epithelial 

 layer. 



Further advanced stages than those just referred to were not 

 discovered except in a single case, which is showai in fig. 25. 

 In this larva, the bodv, still approximately spherical in shape, 

 may measure nearly 100/'- in diameter. An exact measurement 

 can not be made since the larva lies so mixed up in the soft 

 tissues of the choanosome that it is difficult to precisely determine 

 its external limit. Tlie epithelial covering, which should not Ijc 

 wanting until after the larva should have fixed itself on a foreign 

 ol)ject after liberation from the mother body, is entirely concealed 

 from view. Most plainly visible is the hollow skeletal basketwork. 



