120 Dr. G, C. Wallich on the Value of 



by a narrow pellucid ring. In 'this state it is invariably present in Amoeba, 

 Actinophrys, Spongilla, &c." (Annals, ser. 2. (1856), vol. xviii. p. 221). 



" While the distinguishing character of the nucleus [in A. princeps] to 

 which I have above alluded, consists in the nucleolus being so much ex- 

 tended over the inner surface of the nuclear cell that it passes beyond the 

 equatorial line of the latter, and thus causes the pellucid halo which is 

 seen round the nucleus of other Amoebce to be absent ; that is, the nucleolus, 

 being circular and of much less extent than the hemisphere of the nuclear 

 capsule, in most AmcebcB, causes it to appear in them as if surrounded by a 

 transparent area." (Annals for July, 1863, p. 31.) 



"The nucleus in A. princeps, as before stated, differs in appearance from 

 that of all other freshwater Rhizopods that I have examined in the absence 

 of a pellucid area round the nucleolus." (Annals, July 1863, p. 39.) 



Here we find the term nucleus at one time applied to the 

 nuclear capsule, at another to the granular body lying within 

 it ; whilst, on the other hand, the whole of the granular body is 

 at one time termed the nucleolus, at another the clear space 

 within it receives that name. There can be no doubt that a 

 vast deal of confusion has arisen here as elsewhere in referring 

 to the nucleolus as if it were always a distinct portion of the 

 nuclear structure, endowed with some distinct function. As 

 referred to in my descriptions, the term nucleolus simply im- 

 plies the central portion of the nuclear body, rendered more 

 diaphanous than the marginal part by the partial or total ab- 

 sence of the granules, and the crowding of these bodies around 

 the circumference. 



Mr. Carter's views with reference to the feasibility of deter- 

 mining the appearances of so small an organ as the nucleus of 

 Amceba, or tracing specific characters, where the specimen is 

 small, are so diametrically opposed to all my experience that 

 they demand careful examination. He says, '"Whether" the 

 nucleus, before the period at which the creature has attained 

 the T-fo-th of an inch in length, " is circular and presents the 

 usual pellucid area around it, or not, I do not pretend to deter- 

 mine, but I think it very likely; and then this state and the 

 smallness of the Amceba would preclude all possibility of specific 

 distinction ; hence I do not think that there is any necessity for 

 us to concern ourselves about the appearances. At this period 

 the nucleus is not larger than a human blood-corpuscle, and the 

 consistence of the nucleolus apparently homogeneous, that is, 

 without granules, and composed of a fine delicate yellowish film 

 of transparent plasma, in which state it continues, with the ex- 

 ception of increasmg in bulk, up to the time when the Amoeba 

 has attained about one-tenth of the adult or maximum size, that 

 is, about -2-3-oth of an inch long." 



Whatever difficulty Mr. Carter may have experienced in deter- 

 mining the minute characters of organisms not larger than a 

 human blood- corpuscle, I repeat that I have, over and over 



