528 



SYSTEMATIC HISTOEY OF THE INFUSOKIA. 



the quaint terms " daugliters " and 

 *' grand-daug'liters " for the "primary" 

 and '^ secondary " generations or gemm?e 

 of the parent globe of the Volvox : — 

 '' Adult form. — Globular, slightly ovoid, 

 consisting of three generations or families 

 within one another ; containing generally 

 eight daughters, in each of which there 

 are generally eight grand-daughters in- 

 cUstincUy visible. Daughters confined to 

 the posterior three-fourths of the sphe- 

 roid, the anterior fom*th being empty. 

 Progressing with the empty end for- 

 wards. Daughters rotating (this marks 

 the adult foi-m here also) in their cap- 

 sules respectively, which are fixed to the 

 internal periphery of the parent. Grand- 

 daughters small and indistinct, motion- 

 less, and fixed to the internal periphery 

 of the daughters respectively. Peripheral 

 cells conical and biciliated, not uniciliated 

 as figured by Ehrenberg. 59-1880" long 

 and 54-1880" broad." 



In his subsequent remarks, he makes 

 it the specific point of difierence between 



the primary gemmse of this V. steUutus 

 and V. Glohator, that those of the former 

 begin to undergo duplicative subdivision 

 almost immediately after they appear, or 

 " at the time when they do not exceed 

 three times the diameter of the peri- 

 pheral cells," or 1-2700", instead of "not 

 passing (as in V. Glohator) into small 

 cells until they have arrived at more 

 than the 1-300" in diameter." He also 

 alludes to difierences between these two 

 species in the form of the spermatozoids 

 and the mode of fecundation. We ven- 

 ture to remark that if these latter par- 

 ticidars are sufficient to indicate specific 

 differences, it is not so with the size of 

 vegetable cells at which fission may 

 commence. The history of all the sim- 

 plest cellular organisms we know of 

 shows that the period of cell-life, and 

 therefore the dimensions of the cells at 

 which it occurs, stands in no constant 

 relation with the act of fission. The 

 size of a cell and the proclivity to fission 

 depend much on external conditions 

 affecting its vital activity. 



The following genera are distinguished by Perty : — 



Genus SYNAPHIA (Perty), — Corpuscles from 10 to 12, aggregated together 

 within a spherical gelatinous envelope, in mutual contact, so as to form a 

 compact mass. The corpuscles, each furnished with a single filament, arc 

 not spherical but angular and wedge- or pear-shaped, with the wide end 

 turned towards the pheriphery. In very exceptional specimens the gonidia 

 are somewhat separated from each other. Length of filament equal to, or 

 1^ the diameter of the corpuscle, and very fine. The relation between 

 Gonium and Pediastrum has been noted by Cohn and other observers ; but- 

 that between this newly- constituted genus of Perty and the second-named 

 group is much more striking, whether the description given or the illustrative 

 figures be considered; indeed the impression forces itself upon us, that 

 Synaphia is simply a form of Pediastrum. This impression is moreover 

 strengthened by the fact mentioned by Perty, that the movement of the 

 organism, and the fine filament, disappear as the organism advances in age 

 and dimensions. 



Synaphia Dujardinii (Perty). — Cor- 

 puscles clear green to dark or blackish 

 green, measuring within the enclosing 

 envelope 1-1300" to 1-360", more com- 

 monly fi'om 1-720" to 1-480". Move- 

 ments torpid or tolerably quick, around 

 one or other axis, always oscillating. 

 The filaments are only visible when the 

 spherical colony is at rest. The radi- 

 ating grouping of the individual gonidia 

 is not completely sjTumetrical ; some- 

 times the spherical figure is exchanged 



for an ellipsoid. The gelatinous envelope 

 varies in breadth, is clear and trans- 

 lucent, rarely having a red blush under 

 the microscope, and, in large specimens, 

 frequently divided by fine lines into 

 two or three halos. When d}dng, the 

 several corpuscles detach themselves, and 

 after death do not undergo diflluence, 

 but turn yellow and idtimately dissolve 

 away. Frequently a green granule is 

 visible internally, and a scarcely-dis- 

 cernible red point. 



Genus HIRMIDIUM (XIX. 15) (Perty).— A chain of from 4 to 8, very 

 small rounded corpuscles of a pale green colour, siuTounded by a gelatinous 



