80 C. F. MARSHALL. 



I shall now take the chief groups of the animal kingdom in their 

 zoological order, describing the muscle found in each case. 



Structure and Distribution of Muscle in the Animal 

 Kingdom. 



Protozoa. 



Amoeba. — Klein* states, on Heitzmann's authority, that under 

 suitable conditions the protoplasm of the white blood corpuscles 

 can be seen to contain an intracellular network composed of fine 

 fibrils. Dr. Klein has, however, recently informed me that he does 

 not find an intracellular network in Amoeba, nor in the majority 

 of white blood corpuscles. 



On examination of very large specimens of Amoeba pinceps in the 

 fresh state, the constant flowing movement of the protoplasm renders 

 it difficult to conceive of any permanent intracellular network. I 

 have, moreover, made gold preparations of these Amoebae in the 

 following manner : The Amoeba was placed in a drop of water with 

 a little cotton wool underneath the cover glass to prevent the 

 animal being washed away by the reagents. A few drops of 1 per 

 cent, acetic acid were then run in under the cover glass for a few 

 seconds. Gold chloride was then run in, and the animal left in this 

 for fifteen minutes. Formic acid was then added, and the animal 

 left exposed to light for about one hour ; by this time the gold was 

 reduced and the animal stained. The preparation was then mounted 

 in dilute glycerine. 



Amoebse prepared in this way showed no trace of an intracellular 

 network ; the protoplasm simply presenting a mottled granular 

 appearance. 



Although there is no definite intracellular network, comparable to 

 that of an ordinary epithelial or gland cell, known to exist in any of 

 the Protozoa, yet a vacuolated condition of the protoplasm is well 

 known to occur in many of them. This attains a high degree of 

 development in many forms, e.g., Noctiluca. These vacuoles are 

 certainly not all food vacuoles, and may possibly indicate the starting 

 point of the differentiation of an intracellular network, i.e., a differen- 



* "Atlas of Histology," p. 2, diag. 1. 



