74 C. F. MARSHALL. 



acid. I therefore tried various strengtlis of acetic and formic 

 acid in place of the arsenic^ and found the best combination 

 Mas the following : 



Acetic acid 1 per cent 20 parts. 



Gold chloride 1 per cent. ... 4 „ 



Osmic acid 1 per cent 1 „ 



The muscle-fibre was placed in this solution for fifteen 

 minutes, after previous immersion in acetic acid 1 per cent, 

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

 chamber for one or two hours. 



1. Dytiscus. — Fresh muscle-fibre of Dytiscus stained by 

 the above method shows the muscle-corpuscles in the form of 

 one or more chains of nuclei in the substance of the fibre, the 

 nuclei being surrounded by a small amount of undifferentiated 

 protoplasm. The transverse networks are seen directly con- 

 tinuous with the nuclei. This is well shown in fig. 1. Fig. 2 

 shows a portion of fibre with two rows of muscle nuclei ; the 

 transverse networks are seen to be connected with both sets of 

 nuclei in some places. Fig. 3 shows several isolated nuclei 

 with the transverse processes attached to them. 



Transverse views of the network and nuclei are more diffi- 

 cult to obtain. Fig. 4 shows a transverse view of an isolated 

 nucleus, with part of the transverse network connected with it. 



2. Dragon-fly. — The muscle-corpuscles of the muscle- 

 fibre of the dragon-fly are situated peripherally, i.e. just 

 under the sarcolemma, contrary to the general rule in insects. 



In one preparation of this muscle I could trace the trans- 

 verse networks into the muscle-corpuscles ; and, moreover, the 

 networks appeared to be distinctly connected with the intra- 

 nuclear networks of the muscle-corpuscles (fig. 5). 



3. Crayfish. — In a preparation of crayfish muscle pre- 

 pared by Retzius' method I could apparently trace the 

 connection of the muscle network with that of the muscle- 

 corpuscle. In this case it was somewhat difficult to tell 

 whether the efl'ect was not due to the network lying over the 

 muscle-corpuscle ; but by careful focussing I think the con- 

 nection could be made out (fig. 6). 



