OBSERVATIONS ON STRIPED AND UNSTRIPED MUSCLE. 83 



Structure and Distribution of Muscle in the 

 Animal Kingdom. 



Protozoa. 



Amoeba. — Klein 1 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 

 the Amoeba, nor in the majority of white blood-corpuscles. 



On examination of very large specimens of Amoeba 

 princeps 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 prepara- 

 tions of these Amoebae in the following manner : — The Amoeba 

 was placed in a drop of water with a little cotton wool under- 

 neath 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. 



Amoebae prepared in this way showed no trace of an intra- 

 cellular network; the protoplasm simply presenting a mottled 

 granular appearance. 



Although there is no definite intracellular network, com- 

 parable 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. Noc- 

 tiluca. 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 differentiation of the cell into 

 1 ' Atlas of Histology,' p. 2, diag. 1. 



