VOLVOC-USTEJE 



553 



into the central mass of endochrome ; and they will also retreat 011 

 the mere rupture of the hyaline investment. From these circum- 

 stances it may be inferred that they are not enclosed in any definite 

 membrane. On the other hand, the connecting threads are some- 

 times seen as double lines, which seem like tubular prolongations of 

 a consistent membrane, without any protoplasmic granules in their 



9 **'' 



FIG. 421. Structure of Volvox globtifoi: 



11 



interior. It is obvious, then, that an examination of a considerable 

 number of specimens, exhibiting various phases of conformation, is 

 necessary to demonstrate the nature of these communications ; but 

 this may be best made out by attending to the history of their 

 development, which we shall now describe. 



The spherical body of the young Volvox (fig. 421, No. 1) is 



