PROTOCOCCUS PLUVIALIS. 559 



the history of the development of Protococcus pluvialis, 

 shews how very uncertain such characters are. It cannot 

 be doubted, moreover, that the great diversities exhibited 

 in the above respects, at different stages of its growth, by 

 Protococcus pluvialis, exist also in other Algae, if they 

 were duly sought after, and that researches in other 

 species, from the same points of view as those embraced 

 in the present memoir, would probably reduce very 

 materially the large number of genera and species of 

 Algee. 



Thus we see that a single species, owing to its nu- 

 merous modes of propagation, can pass through a number 

 of very various forms of development, which have been 

 either erroneously arranged as distinct genera, or at 

 least as remaining stationary in those genera, although, 

 in fact, only transitionary stages. Thus the still Proto- 

 coccus cell, (Fig. 2,) corresponds to the common Proto- 

 coccus coccoma, Kg. When the border becomes gelatinous, 

 it resembles P. pulclier (Fig. 70) ; and the small cells, 

 P. minor. The encysted motile zoospore is the genus 

 Gyges granulum among the Infusoria, resembling also, on 

 the other side, P. turgides, Kg. and perhaps, P. versa- 

 tilis, Braun. The zoospores divided into two (Figs. 23, 30), 

 must be regarded as a form of Gyges Upartitus, or of 

 P. dimidiatus. In the quadripartite zoospores, with the 

 secondary cells arranged in one plane, we have a Gonium 

 (Fig. 37). That with eight segments (Fig. 38,) corre- 

 sponds to Pandorina Morum, and that with sixteen, to 

 Botryocystis Volvox (Fig. 44). When the zoospore is 

 divided into thirty-two segments, it is a Uvetta or Syn- 

 crypta (Fig. 40). When this form enters the "still" 

 stage, it may be regarded as a form analogous to 

 Microhaloa protogenita ; this Algal genus is probably, 

 speaking generally, only the product of the Uvetta division 

 in the Euglence or other green forms. The naked 

 zoospores (Fig. 32), finally, would represent the form 

 of a Monad, or of an Astasia ; the caudate variety, ap- 

 proaches that of a Bodo. 



