OBSERVATIONS ON STRIPED AND UNSTRIPKD MUSCLE. 87 



lary substance round the nucleus, and a cortical substance 

 splitting into fibrils. This is also described by Schwalbe 1 in 

 the fibres of Aulostoma. 



Lumbricus terrestris. — Gold preparations of the muscle 

 of the Earthworm show large elongated cells which on close 

 examination show longitudinal lines ; these under the -^q 

 immersion objective present a dotted appearance (fig. 3). 

 At first sight it might appear that we have here the network of 

 striped muscle ; but this is not the case. In the first place, 

 there is no appearance of transverse striation at all; iu the 

 second place, the dots are not arranged transversely but are 

 quite irregular ; lastly, so far as I could observe, the dotted 

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

 cell. 



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 Rotifera striped muscle is well known to 

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

 tainty whether the striation is due to the presence of a net- 

 work or not. Nitsche 1 says that the striation in the retractor 

 muscle of the Polyzoa is not due to any wrinkling of the sar- 

 colemma. The retractor muscle appears to be the only muscle 

 that is striped from Nitsche's observations. 



Striped muscle has been recently described by Haswell 2 in 

 the gizzard of Syllis one of the Polychaete worms. 



Mollusca. 



According to Schwalbe, 3 double oblique striated muscle is 

 present in Solen, Ostrea, and Helix. 



Anodon. — Preparations of the adductor muscle of the Ano- 

 don treated with gold show that the muscle consists of small 

 elongated cells of the unstriped type, showing no fibrillation 



1 ' Kenntniss der Bryozoen,' Heft 2, p. 55. 



2 'Quart. Journ. Micr. Sci.,' 18S6. 

 » 'Arch. f. Mic. Anat.,' 18G9. 



