84 C. J. MARSHALL 



the dotted lines are superficial, and do not extend into the body of 

 the eell. 



One of the so-called "hearts" of the worm was treated in the 

 same way ; the muscle-cells were found to resemble almost exactly 

 the muscle-cells described above. 



In the Polyzoa and Eotifera striped muscle is well known to 

 occur. I have not, however, been able to determine with certainty 

 whether the striation is due to the presence of a network or not. 

 Nitsche* says that the striation in the retractor muscle of the 

 Polyzoa is not due to any wrinkling of the sarcolemma. The 

 retractor muscle appears to be the only muscle that is striped, from 

 Nitsche's observations. 



Striped muscle has been recently described by Haswellf in the 

 gizzard of Syllis, one of the Polychsete worms. 



Mollusca. 



According to Schwalbe,J double oblique striated muscle is present 

 in Solen, Ostrea, and Helix. 



Anodon. — Preparations of the adductor muscle of the Anodon 

 treated with gold show that the muscle consists of small elongated 

 cells of the unstriped type, showing no fibrillation or transverse 

 striation. The muscle treated with osmic acid shows faint fibrilla- 

 tion, but no distinct fibrils. 



Patella. — The Limpet was chosen for an investigation of the 

 structure of the heart muscle. In gold preparations of the ventricle 

 I find the network of striped muscle present (Fig. 5). 



In the heart of the Anodon I could not determine with certainty 

 whether the network was present or not, although faint indications 

 of it were obtained. 



Ostrea. — The adductor muscle of the Oyster consists of two por- 

 tions : a white opaque portion, and a more gelatinous portion. 

 Gold preparations were made of each of. these. The cells of the 

 "white muscle" are large, with clear outlines, and remarkable for 

 the clearness and transparency of the protoplasm. The cells of the 

 " gelatinous muscle " are smaller and less transparent. Neither of 

 these showed any network or fibrillation. 



* " Kenntniss der Bryozoen," Heft 2, p. 55. 

 t " Quart. Journ. Micr. Sci.," 1886; 

 X " Arch. f. Mik. Anat.," 1869. 



