Miscellaueoua. 275 



At tho time of fecundation the bundles of antherozoids arc set at 

 libt-rty ]»y tlic dissolution of the wull of the iintheridium ; they niovn 

 rujiidly in the water, and hasten to fix tliemselves on the female 

 ctt'nohia. There they break up to allow the antherozoids to fecun- 

 date the oospheres ; but I have been unable hitherto to observe tho 

 moment of their penetration. 



After fecundation the oosphercs surround themselves with a thick 

 memltrane with a double contour, which until then was invisible, 

 and rapidly change colour : from a dark green they become yellowish 

 preen, then orange. They then contain a red oily matter and a 

 large quantity of starch. It is this orange colouring which led some 

 observers to believe that there was a third species of VoJuox ( Volvox 

 aurfits, Khr.). 



The ]'ulvoces, male, female, and neuter, seek light, either solar or 

 artificial, and keep near the surface of the water. As soon as the 

 female coenobia are fecundated and the oospores change colour, they 

 are seen to avoid the light and to dej^art from the surface of tho 

 water. It is easy to observe this phenomenon in a glass pan or in 

 a watcli-glass ; the green Volvoces stay on the light side, the others 

 on the diametrically opposite. If the glass is turned they change 

 places resiK'Ctively ; and this transfer is effected in a very short time. 

 The Vol voces with orange oospores move much more rapidly from tho 

 light than the others towards it. The displacement of the Volvoces 

 is owing, as is well known, to the movement of the two vibratile 

 cilia with which each vegetative cell is provided, and which project 

 beyond the gelatinous sphere. Xo change of colour or form can be 

 observed in these cells after fecundation ; we are therefore led to 

 think that it is by a sort of attraction exerted on the green matter 

 that the Voh-oces are drawn towards the light, and that it is by a 

 sort of repulsion exerted on the red matter of the fecundated gyno- 

 gonidia that these same Volvoces afterwards seek obscurity. 



When the VoJvocis begin to appear in the waters whore they, are 

 found, scarcely any but neuter coenobia are met with — that is to 

 say, coenobia enclosing only vegetative cells giving birth by segmen- 

 tation to daughter-colonies. When some time has passed tho 

 number of daughter-colonies contained in each coenobium diminishes ; 

 but there then appear in many Volvoces some androgonidia, which 

 represent abortive daughter-colonies. At this moment wo only find 

 a few female Volvoces not containing any daughter-colonies. When 

 tho Volvoces have thus rejjroduced themselves for a certain time by 

 daughter-colonies, the number of female coenobia is increased, and, 

 some exclusively male ca!no])ia, destitute of daughter-colonies, appear, 

 while the neuter coenobia become very rare. 



It results from these facts that during a certain period the Volvox 

 is multiplied by asexual generation, by scissiparity of a vegetative 

 cell, which by successive segmentations produces a colony of indi- 

 viduals similar to the mother-colony to which this ceU belonged. 

 But a time comes when the vegetative cell uo longer possesses tho 

 property of reproducing itself thus ; it can still divide into segments, 

 and givo birth to a colony of little cells which actjuiro a sexual 

 character ; that is to say, they arc incapable of living separately 



