562 Organic Physics. [July, 



upon the advantage in nutrient relations between the free and the 

 coherent state. In the simplest organisms the new cells remain 

 free. They would derive no advantage from coherence with the 

 mother-cell, and they are fully capable of continuing the species, 

 since they contain all the molecular conditions of the type. Here 

 there is no growth, the whole life process is a reproductive one. 

 In less simplified forms, such as the Foraminifera, both tenden- 

 cies are displayed. Possibly the armored condition of the type 

 renders it advantageous for coherence to continue up to a certain 

 stage, yet independent cells are incessantly budded off. In the 

 highest Protozoa a molecular differentiation seems to arise be- 

 tween the different parts of the single celled organism, and this 

 is probably the primitive stage of the cellular differentiation in 

 the Metazoa. The special molecules of the Infusorian represent 

 the special cells of the Metazoan. In the latter type of animal a 

 considerable degree of coherence becomes absolutely necessary, 

 yet it is probable that in the lower forms free cell formation is 

 very active. There are two purposes to be subserved in the 

 organism, the continuance of individual life and the reproduction 

 of the species. For the one, cell coherence is necessary. For 

 the other, cell freedom. And both of these are favored by the 

 nutrient conditions. The specialized nutriment bathes the cells, 

 and the new cell products can gain nutrition both as coherent and 

 as free cells. But the process of reproduction is not as simple as 

 in the Protozoa. No longer does every portion of the body rep- 

 resent the whole body. The free buds thrown off by the cells into 

 the nutrient fluid represent only a special section of the body. 

 Only by some process of combination can cells be produced con- 

 taining the molecular constituents of the whole body. And it is 

 probable that this combination is a natural resultant of food 

 assimilation by these free cells. They take in nutriment, grow, 

 divide or bud off minute gemnu.les, and these gemmules are 

 taken up as nutriment by other cells. Thus fully generalized 

 cells are produced, capable of existence outside the body, and 

 adapted to develop into a copy of the parent organism. 



As the animal becomes of higher grade the process of tissue 

 formation preponderates over that of germ formation, the num- 

 ber of developing germs decreases and the resolution of the body 



pring becomes less declared. IV 



total i 



partial. In fact, as specialization increases the combm 



