1 3 o COMPARATIVE ANATOMY 



in the two cases are produced by like causes. But the 

 resemblance of the oil-drop to the Amoeba does not end here. 

 Under favourable conditions the former may be seen to move, 

 active circulation of its contained granules takes place, 

 exactly simulating the characteristic "streaming movements" 

 of protoplasm, and it may even emit pseudopodial processes 

 and withdraw them, just as an Amceba does. All these move- 

 ments are to be explained, in the case of the oil and salt 

 mixture, on purely physical grounds, and it has been suggested 

 that the movement of protoplasm is due to and may be 

 explained by the same physical causes as those which bring 

 about similar phenomena in the artificial mixture. The 

 question cannot be discussed here, and the reader who 

 wishes to learn more about the remarkable analogies between a 

 simple chemical mixture and living protoplasm should consult 

 Professor Biitschli's work.* It must be borne in mind, how- 

 ever, that with the pseudopodial movement and a few other 

 phenomena of secondary importance the resemblance between 

 the mixture and the Amoeba, the non-living and the living 

 matter, ends. The droplet of oil and salt does not ingest food, 

 does not assimilate, does not grow and reproduce its kind. 

 The most essential vital phenomena are wanting, and it can- 

 not be said, in any sense, to live. The value of Professor 

 Biitschli's experiments consists in their having opened the 

 way for an understanding of the real structure of protoplasm, 

 and it is evident that the analogy of the oil and salt mixture 

 throws great deal of doubt on the propriety of dividing the body 

 of the Amoeba into endoplasm and ectoplasm. 



That the outer layer is nothing more than a temporary 

 rearrangement of the superficial alveoli is further suggested 

 by the manner in which an Amceba feeds. Like all indisput- 

 able animals it takes into its interior, or, as we say, ingests 

 solid food, consisting of vegetable matter, Oscillaria, Diatoms, 

 and even other Protozoa. These substances may generally 

 be seen in the central part of the cytoplasm, and careful 

 examination shows that the separate food-particles are en- 

 closed in a space filled with fluid, called a food-vacuole. The 

 vacuole, however, is formed subsequent to the ingestion of 



* "Investigations on Microscopic Foams and on Protoplasm," by 

 O. Biitschli. Eng. Trans, by E. A. Minchin. London : A. & C. Black, 

 1894. 



