lf'i6] ^Yilsoll: On the Life-History of a .S'oiV Amoeba 271 



common in old cysts, and his culture had plenty of time after eneyst- 

 ment for the karyosome to break up. 



Flagellates and trophozoites are found with two nuclei close 

 together. No evidence, however, of reduction of chromosomes has been 

 found, and so these must be regarded a.s merely binucleate. produced 

 by failure of the cytopla.sm to divide. The proximity of the nuclei 

 mu.st be purely accidental. 



These facts regardinti' the nuclear conditions and the absence of 

 observed sexual behavior in living material lead us to conclude that the 

 evidence for sexual reproduction in this amoeba is as yet lacking. 



No indication of flagellated gametes as de.scribed by Metealf (1910) . 

 nor anything resembling fertilization like that described by Calkins 

 (1904. 1907, 1909) has been found in Naeglena griiberi. Likewise 

 copulation, as Hedges (1914) observed in an amoeba from a hay 

 infusion has not been found, though possibly the agglomeration 

 phenomenon is suggestive of this process. However, since there is 

 apparently no chromosome reduction accompanying this process it 

 seems that it is only a reaction to en^dronmental changes, and has 

 therefore no reproductive significance. It is possible that the process 

 described by Hedges, also, is not of reproductive significance, but this 

 can be determined only by nuclear behavior which he was imable to 

 follow. From all of which it seems that, even if reduction does take 

 place as shown in Glaser's figures 24-27, all his other figures are not 

 unquestionably maturation stages. 



D. COMPARISON WITH RELATED AMOEBAS 



Valdhampfia calkensi (Hogue, 1914) is similar in some respects to 

 the species investigated here. Endogenous buds are formed in multi- 

 nucleate individuals as in Naegleria gruberi, except that in the former 

 two nuclei may sometimes be cut off in one bud. a condition which 

 has not been found in the latter. Exogenous buds are produced in 

 individuals in which chromidia, formed at the expense of the karyo- 

 some, are found. 



Miss Hogue says that division is amitotic and mitotic. In the 

 former her figures resemble stages found in reorganizing nuclei of 

 Naegleria gruberi, an interpretation which has been discussed under 

 amitosis. The latter she says is by promitosis, but she does not give a 

 complete series of this, and the ones .she does give do not seem to be 



