OF THE VOLTOCrNA, 



527 



Dujardln was unable to detect more than one filament ; but Ehrenberg's 

 description of two is now amply coiToborated. 



The structui'e of Volvox has received the careful study of many eminent 

 microscopists, who have been compelled to differ largely from Ehrenberg in 

 their accounts of it. The resume given in the general history of Phytozoa 

 renders it perfectly unnecessary to repeat in this place the particulars of the 

 organization of the members of this genus or to enter into the discussion 

 respecting their true nature as organic beings. 



VoLVOX Glohator (INI.) (xx. 32-47) rent difference between them consistinor 



(p. 180 et seq.). — So called from the 

 globidar figm-e of the aggregate mass or 

 colony constituted by the individual 

 mona'difonn beings or gonidia. When 

 blue or red coloming matter is mixed 

 with the water, strong currents may be 

 observed under the microscope aroimd 

 each globe, which, when in motion, 

 always proceeds with the same part 

 foremost, xx. 32 represents a large 

 globe -^dth eight smaller ones (termed 

 by Ehrenberg, sisters) within it. xx. 34 

 is a section of a globe, more magnified. 

 xx. 35 represents three gonidia in situ 

 within the common envelope. In 

 shallow pools of clear water, in spring 

 and siunmer. The largest globes mea- 

 sure 1-30" in diameter ; the smallest 

 free swimming ones 1-360" to 1-240". 

 Size of a single corpuscle 1-3500". 



Ehrenberg notified the peculiar occur- 

 rence of living Rotatoria within the 

 globes of the Volvox Glohator. Mr. John 

 WiUiams has communicated {T. 31. S. 

 1851, iii.) an interesting observation, 

 confirming Ehrenberg's account. 



Within the cavity of a large specimen 

 of this species, evidencing its usual 

 vitality, and the ciliary movements on 

 its surface, he noticed a very active 

 Rotifer, which he believes to have been 

 the Kotommata parasitica, and which 

 was subsequently accompanied by 

 another of the same species, t3ut smaller. 

 He adds, " By the most careful examina- 

 tion, no opening coidd be perceived by 

 which they coidd have been introduced ; 

 neither did there appear to have been 

 any viscera by which their motions 

 might be impeded, as they swam about 

 as freely as fish in a glass globe, to 

 which, indeed, they bore no faint resem- 

 blance." 



The two following species, named V. 

 aureus and V. stellatus, ai*e, in the opinion 

 of Profs. Busk, Williamson, and Perty, 

 merely developmental phases of V. Glo- 

 hator — V. stellatus being the later stage. 

 " V. aureus''^ says the A\Titer first named 

 (op. cit. p. 32)," exhibits precisely the same 

 structure as V. Glohator, the only appa- 



in the deeper green colom' of the internal 

 globes. These, however, soon exhibit a 

 more important distinctive character, in 

 the formation of a distinct cell-weU of 

 considerable thickness aroimd the dark- 

 green globular mass. This wall becomes 

 more and more distinct ; and after a time 

 the contents change from dark green into 

 a deep orange-yellow, and simultaneously 

 with this change of colour the waU of the 

 globule acquires increased thickness, and 

 appears double. 



" The third foi-m, or V. stellatus, differs 

 in no respect from the two foimer, except 

 in the form of the internal globules, 

 which exhibit a stellate aspect, caused 

 by the projection on their surface of 

 numerous conical eminences fonned of 

 the hyaline substance of the outer waU. 

 The deep colour of the contents of their 

 embiyos, and their change uito an orange 

 colour, at once point out their close 

 analog}^ with those of V. aureus. I have 

 no doubt of their being mere modifica- 

 tions of the latter, and I have obsen-ed 

 smooth and stellate globules in the in- 

 terior of one and the same parent globe.'' 



Mr. Carter, however, does not share 

 this opinion with reference to V. stellatus, 

 which he treats {A. N. H. 1859, iii. p. 6) 

 as a distinct species. 



These extracts from recent and well- 

 known authorities are further valuable 

 as supplying an explanation of Laurent's 

 statements that two sorts of reproduc- 

 tive bodies appear in the globes of Vol- 

 vox. Little weight is attached to this 

 gentleman's microscopical researches, 

 which are mostly ideal. 



V. aureus. — Green, nearly globular. 

 The small secondary globes within them 

 are of a golden colom*, and smooth sur- 

 face. In rain-water standing on tmi. 

 Diam. of globe 1-30". 



V. stellatus. — Small, subglobose, some- 

 times oblong, or of an augidar form, and 

 gTeen colour. The contained globes 

 within them are of a green colour, and 

 have their surfaces tuberculated or stel- 

 lated. Diam. of globe 1-30". 



Carter, who accepts this species, de- 



