36 SURVEY OF THE REPRODUCTIVE PROCESS 



Among the Floridese or rose-coloured algae a group ex- 

 clusively marine we find commonly three different kinds 

 of fructification, situated mostly on separate fronds : 



1. Tetraspores, considered as gemmae by Thwaites, 

 Harvey, Berkeley, and Pringsheim, and consisting of qua- 

 ternary aggregations contained in receptacles, which are in 

 some cases simply imbedded in the frond. 



2. Antheridia, containing, in special receptacles, par-, 

 tides which have been taken for antherozoids, though desti- 

 tute of cilia, and perhaps also of motile, power. 



3. Conceptacles, containing clusters of sporoid bodies, 

 which are generally regarded as the germs or true spores. 



Pringsheim, however, is inclined to think that the last- 

 mentioned bodies at least in some species of Ceramium 

 are rather gemmae, which develope prothallia for the pro- 

 duction of the real q;erms, as he has seen them begin to 

 germinate while still in the conceptacle, before any perfora- 

 tion had taken place for the entrance of antherozoids, and 

 observed that the result was an irregular cellular growth, 

 quite different from the ordinary frond. In this view the 

 prothallium, though unisexual like that of CEdogonium, 

 would differ in representing the opposite sex, bearing not 

 spermatic but germinal particles, whose impregnation would 

 be effected by the rod-shaped antherozoids formed directly 

 on the male frond. 



The constancy of the occurrence of three forms of repro- 

 ductive organs, just noticed on different plants, gives a 

 certain probability to the idea of an alternation of forms, 

 like that occurring in some species of animals the fronds 

 originating from fertilized germs bearing only gemmae (tet- 

 raspores), which, in turn, would develope other fronds 

 maturing true sexual organs. 



In most of the littoral group of fucoids or olive-coloured 

 seaweeds, antherozoids and proper germs have now been 

 detected, generally in separate receptacles on the same 



