MICROSCOPIC FORMS OF VEGETABLE LIFE. 



includes an act of " conjugation," or some other form of the 

 true Generative process ; and as none such has yet been observed 

 in Volvox, there is strong ground to suspect that we are not 

 acquainted with its whole life, but that conjugation may occur 

 in some condition not yet known to us, which may only present 

 itself after a long succession of repetitions of that process ot 

 gemmation, by which the Yolvox spheres are multiplied and 

 reproduced. 



162. Certain curious varieties, however, occasionally present 

 themselves in the preceding cycle. Thus, the young Volvox 

 globe which has attained the size and has undergone the degree 

 of segmentation indicated at G or H, sometimes becomes at first 

 deep green and then yellow; its hyaline envelope acquires an 

 unusual firmness, and a second coat is formed within the first, 

 the colored contents undergoing some retraction ; and eventually 

 a considerable space intervenes between the two coats, which is 

 occupied by a clear fluid. The protoplasmic contents of the 

 inner envelope consist chiefly of starch grains, mixed with a 

 bright yellow and apparently oily fluid. In this and other 

 respects, the body in question corresponds so closely with the 

 "still" or "winter" spore of other Protophytes, which is adapted 

 to resist influences that are fatal to the more actively vegetating 

 forms of these organisms, that it seems most probable (as was 

 first suggested by Mr. G. Busk) to stand in this relation to Vol- 

 vox globator, although the ultimate mode of its development is 

 not known ; and thus the Volvox aureus, as the kind that pro- 

 duces these golden yellow spheres has been designated, is nothing 

 else than an ordinary Yolvox preparing its brood for the winter 

 state of inactivity. The Volvox stellatus of Ehrenberg, again, 

 seems to be nothing more than a variety of the same specific 

 type; its peculiarity consisting in the presence of numerous 

 conical eminences, formed of the hyaline substance only, on the 

 secondary globules, giving them a stellate aspect. The endo- 

 chrome segments resemble those of the globules of Volvox aureus, 

 both in color and composition ; and these two forms of second- 

 ary globules, the stellate and the smooth, having been observed 

 by Mr. Busk to coexist in the very same sphere, are certainly to 

 be regarded as varieties of one and the same type. 1 The same 

 excellent observer has also pointed out the probability, that the 



1 " In the month of August last," says Mr. Busk (Op. cit. p. 44), " when, in a certain 

 pond on Blackheath, there was the most incredible abundance of Volvox, so great, in 

 fact, as to render the water at the lee side of the pond in certain spots of a deep green 

 color, and to cause it to afford, when collected, a very strong herbaceous or confervoid 

 smell, the majority of the plants exhibited the stellate form of spores, or rapidly acquired 

 spores of that character, and very many were in, or soon assumed, the form of V. aureus. 

 They seemed, in fact, to be entering on their hibernating state. Many among them, 

 however, though all small and starved-looking, were of the common kind ; in all these, 

 Prof. Williamson's hexagonal areolation was very distinct. In the month of October, 

 however, upon returning to the same pond, I was able to find very few Volvoces at all, 

 and all of the usual kind; in none of these could I detect the least appearance of the 

 same arrangement." Prof. Williamson has noticed analogous variations, in the speci- 

 mens taken at different seasons from one locality (Op. cit. p. 50). 



