DEVELOPMENT AND VARIETIES OF VOLVOX. 255 



it ; and even in the mature Volvox it continues to form an invest- 

 ment around the hyaline envelopes of the separate cells, as shown 

 in Fig. 11. It seems to be by the adhesion of the hyaline invest- 

 ment of the new sphere to that of the old, that the secondary sphere 

 remains for a time attached to the interior wall of the primary ; 

 at what exact period, or in what precise manner, the separation 

 between the two takes place, has not yet been determined. At the 

 time of the separation, the developmental process has generally 

 advanced as far as the stage represented in Fig. 1 ; the foundation 

 of one or more tertiary spheres being usually distinguishable in the 

 enlargement of certain of its cells. 



197. This development and setting-free of composite Macro- 

 gonidia seems to be the ordinary and characteristic mode of multi- 

 plication in Volvox ; but there are other phenomena which must 

 not be left without mention, although their precise import is as yet 

 uncertain. Thus, according to Mr. Gr. Busk, the body designated by 

 Prof. Ehrenberg Sphcerosira volvox is an ordinary Volvox in a 

 different phase of development ; its only marked feature of dis- 

 similarity being that a large proportion of the green cells, instead 

 of being single (as in the ordinary form of Volvox) save where they 

 are developing themselves into young spheres, are very commonly 

 double, quadruple, or multiple ; and the groups of ciliated cells 

 thus produced, instead of constituting a hollow sphere, form by 

 their aggregation discoid bodies, of which the separate fusiform cells 

 are connected at one end, whilst at the other they are free, each being 

 furnished with a single cilium. These clusters separate themselves 

 from the primary sphere, and swim forth freely, under the forms 

 which have been designated by Prof. Ehrenberg as Uvella and 

 Syncrypta. (According to Mr. Carter, however, Sphcprosira is 

 the male or spermatic form of Volvox r/lobator. See § 199, note.) 

 Again, it has been noticed by Dr. Hicks* that towards the end 

 of the autumn, the bodies formed by the binary subdivision of the 

 single cells of Volvox, instead of forming spherical ciliated Macro- 

 gonidia which tend to escape outwards, form clusters of irregu- 

 lar shape, each composed of an indefinite mass of gelatinous sub- 

 stance in which the green cells lie separately imbedded. These 

 clusters, being without motion, may be termed Stato-spores ; and 

 it is probable that they constitute one of the forms in which the ex- 

 istence of this organism is prolonged through the winter, the others 

 being the product of the true Generative process to be presently 

 described. 



198. Another phenomenon of a very remarkable nature, namely, 

 the conversion of the contents of an ordinary Vegetable cell into a 

 free moving mass of Protoplasm that bears a strong resemblance to 

 the animal Amceba (Fig. 234), is affirmed by Dr. Hicksf to take 



* " Quart. Joum. of Microsc. Science," N.S., Vol. i. (1861), p. 281. 

 + "Trans, of Microsc. Society," n.s., Vol. viii. (1860), p. 99, and 

 " Quart. Journ. of Microsc. Science," N.s., Vol. ii. (1862), p. 96. 



