OBSEEVATIONS ON STRIPED AND UNSTRIPED MUSCLE. 85 



similar, in all respects, to the network described by lletzius 

 and Melland in striped muscle (fig. 2). 



Actinia. — Muscle taken from the base of the Actinia and 

 treated with gold was found to consist of elongated fusiform 

 cells, non-striped, and showing no trace of any intracellular 

 network, or of any fibrillation. 



Hence the conclusions obtained are that in the muscular 

 process of the Hydra cell there is no form of network or fibril- 

 lation, although a network is present in the body of the cell. 

 In the more highly organised Medusa the typical network of 

 striped muscle is found to be present, but in the equally highly 

 organised Actinia no network is present, nor is there any 

 fibrillation in the muscle-cells. 



These results agree with those obtained by Haraann 1 by the 

 method of isolating the cells by maceration in various reagents. 

 He states that the muscles of Hydroid polypes are always 

 smooth, and quite distinct from the striated muscles of the 

 Medusae. Hamann thinks that where transverse striation has 

 been described in Hydroid polypes it is probably due to the 

 action of reagents. 



The Hertwigs, 2 in their observations on the Actiniae, describe 

 no fibrillation in the muscle-fibre. They investigated the 

 tissues of Sagartia and Anthea. 



ECHINODERMATA. 



The muscle of the Echinoderms has been described as striped 

 by several observers. Firstly, by Schwalbe 3 in the muscle- 

 cells between the ambulacral plates of Ophiothrix, and 

 more recently by Geddes and Beddard. 4 From the figure 

 given by the latter observers it is evident that the striation 

 they describe is the false striation mentioned above as being 

 due to annular constrictions. Schwalbe, however, describes 

 double oblique striation. 



1 Loc. cit., p. 20. 



2 ' Die Actiuien." 



3 'Arcuiv fur Mic. Anat.,' 1869, p. 205. 



4 « Proc. Kojal Soc. Edinburgh,' 1873. 



