SOME SPECULATIONS 49 



stages of the evolution of the life-form which it produces. 

 Even so august an individual as the " lord of creation " 

 began existence as a tiny fertilized ovum, and in his 

 foetal development exhibits indications of evolutionary- 

 stages which led up to the human genus. May not the 

 life-history of such a plant as CEdcgonium throw some 

 light on the problem of the origin and development of 

 the vegetable kingdom ? If we did not know from 

 repeated observations that a tiny zoospore developed 

 into a many-celled thallus fixed to a substratum, we 

 could hardly imagine that a ciliated organism, so animal- 

 like in its movements, could lead to such a result. But 

 the fact remains. The thallus itself is but a local 

 habitation for a series of living protoplasts, some of 

 which may become zoospores, others egg-cells, others 

 spermatozoids. Which is the more primitive, the active 

 zoospore or the vegetative thallus ? Must not the 

 thallus have been originally developed from an active 

 organism of which the zoospore is a speciahzed repre- 

 sentative 1 Imagine a one-cell organism which hitherto 

 lived a free existence, multiplying by fission, becoming 

 fixed to some object in water; instead of the cells result- 

 ing from multipUcation, separating, and swimming away, 

 they remain attached in a single row. In such case you 

 have a filament of cells. Any of the cells tend to revert 

 to tjrpe. What wonder, then, that some of them become 

 zoospores ? Nor does it require a great stretch of the 

 imagination to see in the spermatozoid a zoospore 

 sexually adapted. The highly specialized orchid and 

 the sturdy oak arise from microscopic egg-cells fertiUzed 

 by a male cell; therein they seem to betray their lowly 

 origin. But the zoospores and spermatozoids of (Edo- 



