468 



SCIENCE 



[N. S. Vol. XLIV. No. 1135 



iological aspects of organs. For example, the 

 questions on the functions of the corpus 

 luteum in the light of many researches, should 

 have generous treatment in our text-books. 

 The same can be said for the results of re- 

 search in, and for theories on the mechanics 

 of development, experimental embryology and 

 of the field of heredity which is of highest 

 interest to the physician. While these meth- 

 ods and new territories will receive more at- 

 tention in the future, Prentiss's book probably 

 deals sufficiently with them at this time. 



K. J. T. 



CONCERNING THE SPECIES AMCEBA 

 PROTEUS 



While carrying on some experimental work 

 during the past several years with the larger 

 fresh-water amebas, I became convinced of 

 the existence of considerable confusion con- 

 cerning the description of Amoeba proteus, 

 generally regarded as the commonest species 

 of the larger amebas occurring in our fresh 

 waters. 



In order to be sure of the exact nature of 

 the organisms I was working on, which is of 

 course essential in experimental work, I de- 

 cided to look carefully into the matter of 

 species description with the hope of removing, 

 if possible, the confusion I was sure existed 

 here. This work was completed some months 

 ago, but on account of disturbances incident 

 to the great war, the manuscript and drawings 

 reporting the results of this work have appar- 

 ently missed their intended destination — at 

 any rate their present whereabouts are un- 

 known. Since it is uncertain when the manu- 

 script and drawings will be found again, I 

 have thought that the publication at this time 

 of a brief summary of my findings would be 

 welcomed by other investigators of the larger 

 amebas, who also must have felt the need of a 

 reexamination of the specific characters of 

 A. proteus. 



Leidy in 1879 described in detail several 

 species of amebas and to one of these species 

 he applied the name Amoeba proteus, resur- 

 recting Pallas's (1766) old specific name which 

 had been dropped through the influence of 



Ehrenberg. Leidy described the nucleus of 

 proteus as "a thick discoid body, with the 

 broad surfaces somewhat convex, flat, or 

 slightly depressed, and the border rounded." 1 

 Most of his figures show the nucleus a con- 

 cave discoid. 



Penard described Amoeba proteus as possess- 

 ing " always an ovoidal nucleus." 2 



Now a discoid differs fundamentally from 

 an ovoid. A discoid is a solid generated by 

 revolving a semi-ellipse around its short diam- 

 eter as an axis, while an ovoid is a solid gen- 

 erated by revolving a semi-ellipse around its 

 long diameter. 



Penard's proteus is not at all the same 

 species as Leidy's proteus. 



The question therefore is, Is Leidy's descrip- 

 tion adequate? It is adequate. All his figures 

 show discoid nuclei, as may be seen by inspec- 

 tion or by reading the descriptions, with one 

 possible exception, perhaps two: Figs. 3 and 

 4, Plate LI. In these two figures the round 

 or polar view of the nuclei is shown. Al- 

 though these two figures resemble Penard's 

 proteus more closely than they resemble 

 Leidy's typical proteus, there is not sufficient 

 evidence to enable one to be quite sure of 

 their correct species reference. There can 

 be no question then but that Leidy considered 

 the proteus to have typically a discoid nucleus. 



Penard described an A. nitida with a much 

 folded or crushed-in nucleus and says 3 that 

 Leidy's drawing of the proteus nucleus (Fig. 

 9, Plate II.) " represents so characteristically " 

 the folded nucleus of his nitida. But Penard 

 misinterpreted Leidy's figure entirely. Leidy's 

 figure does not show a folded nucleus, but one 

 with a smooth surface, a discoid with slightly 

 concave sides. Moreover, the folded nucleus of 

 Penard's nitida I have found represents an 

 old-age stage of the smooth discoid nucleus of 

 Leidy's proteus. The ectoplasmic ridges and 

 grooves described by Penard as canals in the 

 endoplasm of nitida were also observed by 

 Leidy in proteus. Penard's nitida represents 

 therefore old (or abnormally large) individ- 



i ' ' Bhizopods of North America, ' ' 1879, p. 41. 

 - ' ' Faune Rhizopodique, ' ' 1902, p. 58. 

 3 hoc. cit., p. 61. 



