OBSERVATIONS ON STRIPED AND UNSTRIPED MUSCLE. 85 



Helix pomatia. — Gold preparations of the muscle of the foot show 

 that it consists of very small cells of the unstriped type densely 

 massed together. 



The muscle of the odontophore, however, shows transverse stria- 

 tion, which under the high power is seen to he caused by the presence 

 of the typical network of striped muscle. 



Pecten. — The Pecten differs from most of its class by performing 

 rapid movements of its adductor muscle, whereby ib propels itself 

 through the water. Gold preparations of the adductor muscle made 

 by my friend, Mr. J. T. Cunningham, show the network of striped 

 muscle very plainly (Fig. 4). I have not observed the double 

 oblique striation described b} 7 Schwalbe in the muscle of Molluscs 

 and Echinoderms. As this is not seen in gold and osmic acid 

 preparations, I think it must be an optical effect. Schwalbe, 

 indeed, admits that in Ophiothrix the transverse striation is due to 

 folds in the sarcolemma (loc. cit., p. 211). 



Arthropoda. 



Eepresentatives of the Crustacea and Insecta, viz., the Lobster, 

 Dysticus, and the Bee, were investigated by Mr. Melland,* the net- 

 work, of striped muscle, being found in each case, 



Astacus, Heart-muscle. — Gold preparations of the heart of the 

 Crayfish show the network to be present in this muscle as in 

 the body-muscles ; the network is, however, much finer and more 

 difficult to demonstrate (Fig. 6). 



The muscle-fibres of the heart are intimately blended with what 

 appear to be large masses of granular protoplasm enclosing nerve- 

 cells ; these may possibly be of the nature of nerve-endings. 



Da/pJmia. — As a representative of the minuter forms of Crustacea, 

 I examined the Daphnia. The muscle-fibres of this animal, when 

 examined in the fresh state, only show transverse striation faintly. 

 After many attempts I succeeded in obtaining a satisfactory gold 

 preparation, where the muscle-fibres were much softened and 

 pressed out to many times their normal diameter. Thoso fibres 

 show the network very plainly (Fig. 7). 



In this case the animal was placed whole in 1 per cent, acetic acid 



* Loc. cit. 



