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



in its interior, within which, again, is another cell or transpa- 

 rent area : that is, the nucleolus appears to be composed of its 

 proper cell, then a protoplasm in which its spherules are de- 

 veloped, and then within this again a central cavity filled with 

 some transparent fluid — being now, in fact, only a repetition in 

 structure of the nuclear utricle which surrounds it, and of the 

 vegetable cell generally. 



Out of the fourteen colourless specimens, only two afforded 

 me the opportunity of seeing the effete nucleus, it having pre- 

 viously disappeared in the rest through atrophy, or having be- 

 come destroyed by contact during compression with the rough 

 grains of sand of which the test is composed — a frequent occur- 

 rence in examining the contents of the green specimens. 



One of these effete nuclei represented the description just 

 given; and the other differed from it only in a large portion, of 

 the grumous contents of the nuclear protoplasm still remaining 

 in it, but no spherules, while the nuclear utricle had become 

 ruptured at one point, and a small portion of the nuclear proto- 

 plasm, now presenting a sacciform appearance, entangled in it, 

 to which one of the granuliferous cells above mentioned adhered 

 outside, and so strongly that it could not be separated by any 

 means that would not destroy the whole structure of the nucleus. 

 This granuliferous cell I therefore infer to have been one of the 

 spherules, which was still so far united to the parent protoplasm; 

 but whether the rupture was caused by the pressure to which 

 the nucleus had been subjected, or had occurred naturally, to 

 allow of the passage of the spherules from the nucleus into the 

 body of the animal (as appears to be the case in the process of 

 reproduction in the Ehizopodous cell which inhabits the proto- 

 plasm of Nitella, of which more hereafter), remains to be deter- 

 mined. There was also an appearance, on the external surface 

 of the nucleus, of a minute hole extending through the nuclear 

 utricle to the centre of the nucleolus ; but whether, again, this 

 was caused by the presence of the transparent area in the centre 

 of the spherules of the nucleolus, or by a real hole, I was not able 

 to decide. In much of this examination I was greatly assisted 

 by the use of iodine and sulphuric acid, which, it should be 

 remembered, must be used cautiously, and time given to them 

 to produce their respective effects, or they will fail to elucidate 

 that amount of structure which otherwise may be brought out 

 by their application. 



7. Lastly, surrounding the whole animal portion in one spe- 

 cimen of the colourless Diffiugia, was a tough transparent mem- 

 brane like a capsule, which, tested with iodine and strong sulphuric 

 acid, showed a violet tint, and seemed to have been secreted for 

 the protection of the young ; but, as it only occurred in one 



