STRUCTURE OF YOLVOX GLOBATOE. 253 



curious rhythmical contraction and dilatation at intervals of ahout 

 40 seconds ; the contraction (which seems to amount to complete 

 obliteration of the cavity of the vacuole) taking-place rapidly or 

 suddenly, whilst the dilatation is slow and gradual. This curious 

 action ceases, however, as the Cell arrives at its full maturity ; a 

 condition which seems to be marked by the greater consolidation 

 of the primordial utricle, by the removal or transformation of some 

 of the chlorophyll, and by the formation of the red spot (J), which 

 obviously consists, as in Protococcus, of a peculiar modification 

 of chlorophyll. 



195. Each mass of Endochrome normally communicates with 

 those in nearest proximity with it, by extensions of its own. 

 substance, which are sometimes single and sometimes double 

 (Fig. 5, b, b) ; and these connecting processes necessarily cross the 

 lines of division between their respective Hyaline investments. The 

 thickness of these processes varies very considerably; for sometimes 

 they are broad bands, and in other cases mere threads ; whilst 

 they are occasionally wanting altogether. This difference seems 

 partly to depend upon the age of the specimen, and partly upon 

 the abundance of nutriment which it obtains ; for, as we shall 

 presently see, the connection is most intimate at an early period, 

 before the Hyaline investments of the cells have increased so 

 much as to separate the masses of endochrome to a distance from 

 one another (Figs. 2, 3, 4) ; whilst in a mature individual, in 

 which the separation has taken-place to its full extent, and the 

 nutritive processes have become less active, the masses of endo- 

 chrome very commonly assume an angular form, and the connecting 

 processes are drawn-out into threads (as seen in Fig. 5), or they 

 retain their globular form, and the connecting processes altogether 

 disappear. The influence of re-agents, or the infiltration of water 

 into the interior of the Hyaline investment, will sometimes cause 

 the connecting processes (as in Protococcus, § 189) to be drawn 

 back into the central mass of endochrome ; and they will also re- 

 treat on the mere rupture of the Hyaline investment : from these 

 circumstances it may be inferred that they are not enclosed in any 

 definite membrane. On the other hand, the connecting threads are 

 sometimes seen as double lines, which seem like tubular prolonga- 

 tions of a consistent membrane, without any protoplasmic granules 

 in their 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. 



196. The spherical body of the Jyoung Voir ox (Plate in., Fig. 1) 

 is composed of an aggregation of somewhat angidar masses of Endo- 

 chrome (6), separated by the interposition of Hyaline substance ; 

 and the whole seems to be enclosed in a distinctly membranous 

 envelope, which is probably the distended Hyaline investment of the 

 Primordial Cell, within which, as will presently appear, the entire 



