REJUVENESCENCE IN NATURE. 163 



point in the hinder part of the cell. In Vaucheria clavata 

 I have often seen a separation of the germ-cell into two 

 about equal portions, through a constriction* occurring 

 during the birth between the anterior, already born, and 

 the posterior portion still jammed in the elastically con- 

 tracting mother-cell (the duh). T observed a similar case 

 in Stigeoclonium mbspinosum. A gerin-cell half born, 

 i. e., protruded through the lateral opening of the mother- 

 cell, became constricted by the contraction of the small 

 orifice of the elastic mother-cell, in such a way that the 

 posterior portion could no longer penetrate. The part 

 which had emerged, bearing the cilia, acquired a 

 tremulous motion, which became the stronger the more 

 the constriction cut it off from the posterior imprisoned 

 portion, till at length it hung only by a fine thread. 

 Finally, the born portion broke loose and hurried away, 

 while the unborn piece remained behind in the mother- 

 cell. The entire process lasted some minutes.f 



That the formation of the cell-membrane does not take 

 place until after the cell is separately constituted, is fur- 

 ther shown by all those cases in which the formation of 

 new cells takes place freely and without contact with the 

 membrane of the mother-cell. In the formation of the 

 resting seed-cells of (Edogonium we see the thickish cell- 

 contents, composed of greenish coloured mucilage, mixed 



* See the vivid description which Unger gives of this process (1. c., 

 pp. 23-27). But where tlie author of this interesting treatise asserts that 

 the escape of the germ-cell of Vaucheria is passive, and not a really inde- 

 pendent act, I cannot agree with him. The swelling np of the club before 

 it tears, together with the hemispherical vaulting of tlie lower cross-wall 

 pressed downward in the filament, show clearly that the contents of the 

 club undergoing conversion into the germ-eeU, acquire a development which 

 the firm membrane of the parent-cell cannot follow, so that this is brought 

 into a condition of violent stretching, which results at length in a rupture, 

 and, in consequence of the contraction of the walls, the gradual squeezing 

 out of the germ-cell. 



f (I have observed in a species of Chlamidomonas, while four active 

 gonidia were being set free by the solution of the cellular membrane con- 

 necting them as produced from a resting vegetative cell, one of them divided 

 into two, so that five were produced. I saw the entire process, which 

 occupied about an hour. — A. H.) 



