CIILOROSPEEMEJl. 3 



now been discovered in several, leading to tlie inference tliat they exist in all. In some 

 cases the spermatozoids are directly formed within the cells of the frond, from which they 

 are dispersed in the water, and find their way to the enlarged cell in which the nucleus 

 of the future spore, or rather sporangium, is contained, and which they penetrate, and 

 effect the fertilization of the contents. In other cases there are formed within the cells 

 of the frond and emitted into the water, solitary male-producing bodies resembling 

 zoospores in form, but of smaller size, to which Pringsheim gives the name androspores. 

 These androspores, after swimming freely for some time, like the zoospores, affix them- 

 selves (in (Edogonlum) to the surface of the enlarged cell containing the female nucleus 

 or in its immediate neighborhood ; and then develope into minute frondlets, consisting 

 of two or three cells, the lowest of which contains endochrome, and acts as a mother- 

 cell, while the uppermost becomes an anfheridinm in which spermatozoids are formed. 

 After a time both the female-cell and the antheridium open at the summit ; the sper- 

 matozoid is liberated and enters the aperture of the ovarian cell and fertilizes tlie 

 enclosed nucleus ; from which there results the large, immoveable spore characteristic 

 of the genus. The whole process is described and its various stages elaborately figured 

 in Pringsheim's memoir, republished in a French translation in An. Sc. Nat. 4th ser., 

 vol. 5, p. 250, t. 1.5, to which I must refer for a fuller account. A previous memoir by 

 the same author in An. Sc. A^at., vol. 3, describes the fertilization of the spores of 

 Vaucheria by an analogous process. Various memoirs have also recently appeared by 

 Thuret, and by Derbes and Soliere, describing the process of the fertilization of the 

 spores, and the development of the frond in other classes of the Algje ; and from the 

 large number of species which have been investigated by these excellent observers, we 

 may perhaps be warranted in drawing the general inference, that a process of fertiliza- 

 tion, by two opposing sexes, exists in all the Algte. It certainly exists in the Melano- 

 sperms, Rhodosperms, and in many of the inferior Chlorosperms. There is much variety, 

 however, in the appearance of the antheridla in different classes ; in some no spermato- 

 zoids have yet been discovered, in others they are of considerable size, and very active 

 and well formed. In some cases each spore is separately fertilized ; in others it is a 

 body which afterwards developes spores. One important observation has been made by 

 Pringsheim which is specially interesting from its bearing on the disputed question of 

 the origin of the embryonic vesicle in the higher plants, namely, that in no instance has 

 he observed any growth to proceed from the spermatozoid, but that its function seems 

 to have been performed when its contents have mixed with those of the nucleus ; the 

 spermatozoid itself being wholly absorbed and dissolved in the mass. 



Much still remains to be done in tracing the development of these Algas, more 

 especially in studying the transformations which many of them undergo. Very many 

 have two or three different modes of re-producing the species, as by self-division, by 

 zoospores or gemma;, and by properly fei'tilized spores ; and the individuals resulting 

 from these various modes of growth are not always similar. Thus there is in many an 

 " alternation of generations," to be studied, such as has been noticed among lower 

 animals ; and probably when the subject has been properly worked out, a large number, 

 not only of species, but of genera, especially among the fresh water kinds, must be 

 erased from our lists. It now appears probable to Pringsheim that many of the minute 



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