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If I may keep to the above simile of two umbrellas, the 

 differences and resemblances between protoplasm and the 

 r artificial foams may be summed up as follows. Protoplasm 

 ( from nature's workshop is essentially of exactly the same 

 J structure as the artificial protoplasm from Biitschli's work- 

 j shop, only the former enjoys the agreeable advantage that 

 / the substance of its framework is not olive oil, but the 

 1 peculiar substance of protoplasm, and its enchylema also 

 \^ contains many substances which the latter does not possess. 

 Any one who denies that the phenomena to be observed 

 in the foams may be compared with those exhibited by 

 protoplasm, and may be used for an explanation of them, 

 may also assert with as much reason that everything which 

 has hitherto been stated with regard to the combustion of 

 organic substances in the metabolism of the animal machine 

 is useless, for the animal lives, and consists of a substance 

 protoplasm which is peculiar in the highest degree, while 

 all processes of combustion, as we know, go on in not- 

 living material and without the co-operation of protoplasm. 

 Ktinstler has, however, as was said, adopted my view 

 as regards the general appearance of the structure of the 

 protoplasm. Yet he does not think it necessary to give 

 up entirely his earlier idea of protoplasm being composed 

 of hollow spherules. Thus he tries to render it probable 

 that the lamellae which form the walls of the alveoli may 

 split occasionally, so that single alveoli become isolated as 

 spherules through the appearance of an intervening fluid 

 matrix. This possibility he attempts to demonstrate, 

 more especially by means of observations upon the proto- 

 plasm of a Foraminiferan with a peculiar shell, which has 

 been dealt with already in two works dating from 1888. 

 Without entering more closely into these observations, I 

 should like merely to express my conviction that the little 

 vesicle-like bodies, which Klinstler observed either singly 

 or united into groups in the endoplasm of this Foramini- 

 feran, and described as almost fluid and granulated, have 

 certainly not arisen in the manner alleged by him, through 

 isolation of the alveoli of a protoplasmic network which 

 existed before. My own observations of a former date, as 



