IS Mr. H. J. Carter on Spongilla. 



frequently be seen to be in a pavement of cell-like cavities (if 

 they be not real cells according to Mohl's definition) which lines 

 the inner surface of the cell- wall of the internode. Whether 

 these be mere inflations of a protoplasmic layer, I have not the 

 means by me now to test ; but they multiply by division, like the 

 starch-cell of C/iIamydococcus, kc, like the "nucleus^^ in many 

 instances, and therefore like the plant-cell, — which, with the ap- 

 pearance of a cell-like line of demarcation around them, gives 

 them so much the character of a " cell," that I question whether 

 this term (or that of" utricle'") is not still better adapted for them 

 than the term "chlorophyll-granule" used by Mohl. It seems 

 to me not at all improbable that these cells may be parts of the 

 plant-cell-contents, which have a pellicle over them that isolates 

 them from the protoplasm, just as much as the pellicle on the 

 surface of an Amoeba would isolate it, if similarly situated, and 

 that this pellicle may become evident by hardening as the pro- 

 toplasm within it gradually perishes. However, as before stated, 

 I am not prepared to go into the matter further than for the 

 purpose of correcting the error mentioned, and will therefore 

 conclude by recommending a special study of this organ to those 

 who would advance our knov/ledge of the vegetable cell. 



Turning to another subject, it might also be incidentally ob- 

 served here, that the hroicn discoloration of fresh water, arising 

 from the presence of a multiplicity of Peridinea, to which I have 

 had occasion to allude in noticing the red discoloration of the 

 sea around the island of Bombay, which takes place from the 

 same cause*, occurred in the tank where the sixteen-cell Eudo- 

 rina w'as, to such a degree that in three weeks after their first 

 appearance, viz. on the 15th of August, they had so increased 

 by duplication, as not only to give the water a dark brown 

 colour, but to obscure the bottom where it was not more than a 

 foot deep. 



As regards the Eudorina, they became scanty and disappeared, 

 almost everywhere, by the end of August. 



Spongilla, 



By a reference to my description of the " Ultimate Structure 

 of Sjjongilla-f /' it will be observed that I was not confident of 

 the circular transparent area in the " ampullaceous sac" being 

 an aperture, although it a})peared to me, when situated on one 

 side, to admit the particles of carmine into its interior. These, 

 again, were evidently seen to be drawn in that direction by the 

 presence of cilia, whose motion only became visible when the 

 '' ampullaceous sac" was in the centre of the microscopic field, 



* Annals, vol. i. p. 258, 1858. f Annals, vol. xx. p. 28, 1857. 



