THE BEGINNINGS OF LIFE. 389 



way towards the confines of the Splrogyra cell, which 

 they pierce before any further elaboration of their 

 contents takes place. 



On reaching the cell wall, each form puts forth a 

 minute papillary eminence, which, having passed 

 through the wall, expands into a ^ large sac, or bursts at 

 its apex.' The isolated form gradually drags four-fifths 

 or more of its bulk through the opening, and some- 

 times so much is dragged through as only to leave a 

 little papillary eminence within — so that the portion of 

 protoplasm seems as if it were entering instead of 

 escaping from the Splrogyra cell. Whereas in certain 

 cases where a tubular extension is formed, it expands 

 into a delicate cyst of a flask-like or globular shape, 

 outside the cell wall^ and retains the protoplasmic con- 

 tents here until they are ultimately developed into 

 Monads. These, which are much larger than the 

 Monads developed within the Nitella filaments, on 

 issuing, move about rapidly for a time by the aid of a 

 strong cilium carried in front like tliat of Astasia^ and 

 then become stationary. The vesicula, or 'contracting 

 vesicle," which does not appear before they leave the 

 cyst, now becomes very active, the cilium is gradually 

 diminished in size and altogether disappears, and the 

 '■ Monad passes into a rhizopodous reptant state, which 

 afterwards becomes actinophorous, and finally assumes 

 a form indistinguisliable from that oi Actlnophrys soU 

 The developmental changes taking place within these 

 outgrowtlis, and the subsequent changes which the pro- 



