358 Mr. H. J. Carter on Difflugia pyriformis. 



lating towards one, and one towards two, or the whole of the 

 contents of one cell going over to mingle with those of another, 

 to form the rounded or elliptical spore, as the case may be; or 

 a portion only of the contents doing this, that is, the mass ulti- 

 mately becoming unequally divided, while each portion assumes 

 the rounded spore-form in its respective cell; or an arrest of the 

 process after union of these contents, when the two portions re- 

 main connected by an isthmus band through the tube of inter- 

 communication ; or, finally, the contents of each cell assuming 

 the spore-like form in their respective cells, without ever min- 

 gling at all, &c. Nay, I have drawings of a Spirogyra trying to 

 tubulate with the cells of a filament of Cladophora, — that is, 

 the tube of intercommunication of the cells of the filament of 

 the Spirogyra respectively being projected against those of the 

 Cladophora, but ending upon the latter in a bunch of csecal 

 tubuli which present a rootlike appearance in each instance. 



I have not data to state, as before mentioned, whether, in the 

 conjugation of Difflugia pyriformis, the whole of the contents of 

 the two individuals normally remains in one test or not ; for, 

 in the instance mentioned, although this was the case at first, 

 the contents, as I have stated, subsequently became very un- 

 equally divided; nor have I found a sufficient number of the 

 empty tests among the filled ones to indicate this ; but as regards 

 the union of more than two tests together throwing doubt upon 

 the view that such is a true act of generative conjugation, we 

 have seen that there is just as much variety in the conjugation 

 of the cells of Spirogyra, where the conjugation is undoubtedly 

 part of the process of reproduction. Whether the spore-shaped 

 contents of the cells of Spirogyra, which thus appear to be im- 

 perfectly formed, ever germinate, has not, to my knowledge, 

 been determined. I should think that at least the smaller 

 portions became abortive. 



Lastly, we have to consider the import of the small spherules 

 of the nucleolus. Formerly, I thought that they might be 

 sperm-cells, or impregnating-agents, when studying the germi- 

 native process in the Rhizopodous cell that inhabits the proto- 

 plasm of Nitella (see good drawings of this cell, and a descrip- 

 tion of them, in 'Annals,^ vol. xviii. p. 237, pi. 7. figs. 93-98) ; 

 but on looking over my sketches of this cell in connexion with 

 what I have lately witnessed in the nucleus of Difflugia pyri- 

 formis, it seems to me that the '"^ protoplasmic zone,^' which in 

 this instance becomes mulberry-shaped, and which I then sup- 

 posed to be developed around (outside) the nucleus, should 

 have been regarded as homologous with the protoplasm in 

 which the spherules of Diffiugia are developed — that is, as the 

 nuclear protoplasm. Certainly, here, in the Rhizopodous cell of 



