150 COHN, ON VOLVOX GLOBATOR. 



two motile cilia^ and may be compared with a Chlamydococciis. 

 The green endochrome is suspended, as it were, in the caA^ty, 

 being connected with the waU only by means of filiform 

 processes. 



Like all the Algee, the Volvocinece present two distinct 

 modes of reproduction ; but up to the present time naturalists 

 have been acquainted with only one of these, consisting in 

 the repeated segmentation of the constituent cells, and re- 

 sembling the fissiparity of Chlamydococcus and Gonium, or 

 that of most of the Palmellacese, 



The second mode of reproduction of Volvox requires a 

 sexual conjunction, and is not observed indifferently in all 

 individuals. The spherules, endowed with the sexual fimction, 

 are distinguished by their volume and the more considerable 

 number of their component utricles ; they are generally 

 monsecious, that is to say, they enclose at the same time male 

 and female cells, although the majority of their contents are 

 neuter. The female cells soon exceed their neighbours in size, 

 assume a deeper green colour, and become elongated like a 

 matrass towards the centre of the Volvox. The endoclirome 

 of these cells does not undergo fission. In other cells, on the 

 contrary, which acquire the size and form of the female cells, 

 the green plasma may be seen to divide symmetrically into 

 an infinity of very minute particles, or linear corpuscles 

 associated into discoid bundles. These are furnished with 

 vibratile cilia, and oscillate, at first slowly, in their prism, but 

 the movement soon becomes more active, and the bundles 

 speedily break up into their constituent elements. The free 

 corpuscles are very agile, and it is impossible to regard them 

 as anything but true spermatozoids ; they are linear and 

 thickened at the posterior extremity ; two long cilia are placed 

 behind their middle, and the rostrum, which is curved like 

 the neck of a swan, possesses sufficient contractility to execute 

 the most varied movements. These spermatozoids, so soon 

 as they are able to disperse themselves in the cavity of the 

 Volvox, quickly crowd around the female cells, into which 

 they eventually penetrate ; arrived there, they attach them- 

 selves by the beak to the plastic globule, destined in each cell 

 to form a spore, and with which they are gradually in- 

 corporated. Fecundation having been thus effected, the re- 

 productive globule becomes enveloped successively by an in- 

 tegument exhibiting conical pointed eminences, and by an 

 interior smooth membrane ; the chlorophyll which it con- 

 tained is now replaced by starch grains, and a red or orange- 

 coloured oil. This is the condition of the spore at maturity, 

 and occasionally forty of these bodies may be counted in a 



