100 C. F. MARSHALL. 



were discussed with him, and the preparations submitted to his 

 examination. My thanks are also due to Dr. Klein for kindly 

 showing me his preparations and for examining several of my own. 

 I must also thank Mr. J. T. Cunningham for the use of the Scottish 

 Marine Station, and for obtaining several of the animals. 



DESCRIPTION OF PLATE VI. 



Illustrating Mr. C. P. Marshall's paper on "Observations on the 

 Structure and Distribution of Striped and Unstriped Muscle in 

 the Animal Kingdom, and a Theory of Muscular Contraction." 



In all cases the gold chloride used was 1 per cent., the formic acid 

 25 per cent. The " usual gold method," when stated, means 1 per 

 cent, acetic acid for a few seconds, gold chloride thirty minutes, 

 formic acid twenty-four hours in the dark. 



Fig. 1. Ectoderm cell of Hydra : gold preparation. (1 per cent. 



acetic acid for a few seconds, gold chloride thirty minutes, 



formic acid one hour, exposed to sun.) a. Intracellular 



network, b. Muscular process, c. Intranuclear network. 



^ immersion obj. 

 Fig. 2. Portion of muscular fibre of Medusa. Usual gold method. 



-^ imm. obj. 

 Fig. 3. Portion of muscle-cell of Earthworm, showing longitudinal 



rows of dots. Usual gold method. -^ imm. obj. 

 Fig. 4. Muscle-fibre from adductor of Pecten, showing network. 



Usual gold method. ^ imm. obj. 

 Fig. 5. Muscle-fibre from heart of Patella. (Acetic acid, 5 per cent, 



two minutes, gold thirty minutes, formic acid two hours, 



at 40°C.) Zeiss, J obj. 

 Fig. 6. Crayfish heart, Gold preparation of. (Acetic acid, 5 per 



cent., a few seconds, gold twenty minutes, formic acid one 



hour, at 40°C.) } obj. 

 Fig. 7. Muscle-fibre of Daphnia. (Acetic acid, 5 per cent., ten 



minutes, gold thirty minutes, formic acid two hours, at 



40°C.) yq imm. obj. 

 Fig. 8. Muscle of Bird (left in formic acid three days). -fa imm. obj. 



