INFUSOKIAL ANIMALCULES. 67 



beings congi-egated in masses, when a general analogy" may be traced 

 between them and the polypes, grouped together, in the structure of 

 the sponges. Associated groups of monads are met with in the 

 family Volvocina, where each individual contributes to the growth of 

 the whole mass, as in the sponge. 



Since writing the above, we have met with the excellent essay of 

 M. Thuret, (Op. cit.) in which he discusses the aflfinity of the Zoos- 

 pores of Algae with Infusoria (Pohjgadrica.) He whites : " Their 

 organization presents great analogy with that of Infusoria. The 

 disposition of the cilia is the same in Pheosplwrce (a division of the 

 Algae) as in Ccrcomonas and At/qjliimonas, of Dujardin. But it is 

 between the reproductive bodies of Conferva3, and certain Infuso- 

 ria, coloured green, that the greatest resemblance subsists. I allude 

 to the Diselmis viridis, (Duj.,) the Chlamidomonas puhisculus, of 

 Elu-enberg. In the form of the body, in that of the flabcUi- 

 foiTU cilia, and in the disposition of those cilia, as also in the contents 

 of the body, the resemblance is complete. The movements of 

 Diselmis are like those of Zoospores, and, like them, they tend to the 

 light. In one distinct species, or rather, in a particular state of the 

 same species, a very clear red spot is discernible, and a central globule, 

 very Hke, in appearance, to the amylaceous graniiles, so fi'equcnt iu 

 the cells of green Algoe. These Infusoria appear to act on the 

 atmospheric air, like Algae, and the green parts of other plants, dis- 

 engaging a gas (oxygen?) imder the influence of light. They ex- 

 hale an evident spermatic odour. Their reproduction occiu's by 

 spontaneous division; 2-43'oung ones being formed within the common 

 integument. I have observed the same mode of reproduction in the 

 Eiiglence, which act on the air, and turn to the light, like Diselmis, 

 but have an extremely contractile body, changing its figure every 

 moment, which will not admit their being confounded with Zoospores, 

 and leaves no doubt of their animality. This binary or quaternary 

 division is met with also in the various species of Tetraspora, which, 

 though ranged with the Algae, appear to me of very doubtful 

 vegetable nature. In Tetrasjjora gelatinosa, I have recognised green 

 globules, disposed in fours, and each furnished with two cilia of 

 extreme length, wliich are lost in the gelatinous mucus, of which 

 the frond of this supposed plant is constituted. AU these produc- 



