OBSKRVATIONS ON STRIPED AND UNSTRIPED MUSCLE. 81 



due to the presence of the intracellular network, described by 

 Retzius, Bremer, and Mellaud. 



I have examined muscle taken from representatives of the 

 chief groups of the animal kingdom with the special object of 

 investigating the presence of an intracellular network in the 

 muscle-cells, either such as that of the striped muscle-fibre, 

 or, when this does not exist, an intracellular network of any- 

 kind. 



The Amoeba and Hydra have been included in this investiga- 

 tion ; for it is an important point to determine the existence 

 of an intracellular network in such a primitive and eminently 

 contractile cell as the Amoeba; it is also important to in. 

 vestigate the structure of the muscular processes of the ecto- 

 derm cells of the Hydra, as they are supposed to represent the 

 first beginning of a muscle-cell. 



In all cases the outlines and main details of the figures 

 were drawn with the camera ; in most cases under the -^th 

 immersion objective of Beck with No. 2 eyepiece, giving a 

 magnifying power of 1100 diameters. 



Methods of Preparation. — The chief method of pre- 

 paration used was the method of gold staining employed by 

 Melland. The gold stains and renders evident the intracellular 

 network of most cells, especially the network of the striped 

 muscle-cell ; hence it is at once a test whether the striation of 

 the fibre is due to the presence of the network, or whether it 

 is merely the false striation mentioned above. 



Various modifications of the gold method were employed 

 according to the delicacy of the tissue under investigation. 

 The method employed by Melland consists in placing the 

 muscle in 1 per cent, acetic acid for a few seconds ; then 

 in 1 per cent, gold chloride for thirty minutes; then in 

 formic acid, 25 per cent., for twenty-four or forty-eight hours 

 in the dark. 



This answers well for vertebrate and insect muscles. But 

 for the more delicate organisms, such as the Hydra, Daphnia, 

 &c, and the heart muscle of invertebrates, I found a one 

 hour's immersion in formic acid, exposed to strong sunlight, 



VOL. XXVIII, PART 1. NEW SER. F 



