42 PROFESSOR DUNF! ON THE 



the lowest holds what it cannot share with the highest is not. 

 The element in the foraminifer which determines pattern 

 separates it, not only from forms high in the zoologic scale, 

 but also from the low forms next to it. And the adaptive 

 principle reigns here, because one side of specific rank 

 includes what an animal holds of matter disposed in it as in 

 no other ; and another side, what it holds of vital force under 

 the same limitation ; and yet another, what it holds of 

 psychical quality regarded from the same point of view. 

 These are the features which the theoretical factor is said to 

 influence, to modify, to change, and to re-dispose> in order to 

 new forms altogether. Does it succeed ? Has it ever in the 

 knowledge of science succeeded ? Perhaps the following 

 . brief notes on Drfflugia prote'/'foo'onis (Ehrbg.) may indicate 

 the direction of the answer to these questions. Thi>i 

 species belongs to the Lohosa, the simplest sub-order oi' 

 Rhizopoda, and consists of two layers, a gelatinous granular 

 endoplasm and a pseudo - membraneous exoplasm, with 

 flattened pseudopodia. It is not the lowest of the group. 

 Frotamoeha (Haek.), Amoeba (Ehrbg.), and Arcella (Ehrbg.) 

 represent the forms which lead up to it, but they are distinct 

 fi-ora it. D'lflugia is referred to because it illustrates in 

 a striking way the limitation of the energetic metabolism 

 characteristic of this group. Though the embryonic type 

 developes in the direction of fvoteiformis and reaches its 

 mature state, it is not limited to this groove. It may pass 

 through stages of growth each of which ends in a mature form, 

 very unlike -prote'ifovmis, yet in reproduction they return to 

 its embryonic type, while, as sub-species, they have well- 

 marked habits of their own, and differ in two important 

 respects, — selective capacity as to food, and adaptive capacity 

 as to covering. Diff/iigia lafjenijormis, for example, covers 

 itself with minute bits of mica, or other thin, glistening 

 mineral, with an exactness which scarcely leaves the least 

 vacant space between them, and even, in many instances, 

 seeming to fit broken edge into broken edge. It is hard 

 to find words suited to the phenomena of shape and of habit, 

 because the ordinary terms, — skill, selective instinct, discri- 

 mination, choice of material, and the like, — are apt to 

 convey meanings which imply more than the phenomena. In 

 the development, succession, definite individuality, and 

 characteristic covering of the sub-species, we have features 

 ever recurring in orderly sequence throughout their genera- 

 tions ; and all this points to a repetition of adaptations, so 

 many and so nice, that to ascribe them to mere unguided 



