BIHAKG TILL K. SV. VET.-AKAD. HANDL. BAND. 3. N:0 13. 5 



elevations (23), and it is between these warts tliat the above 

 mentioned spiues are situated. Some of these are smaller 

 (0,1 mm. long, 0,004 mm. broad) and appear merely as roun- 

 fled bristles, slightly bent, without any cavity (21, 23), others 

 are considerably larger, nearly straight(0, i mm. long, 0,0 1 mm, 

 broad) with a lougitudinal groove (20), out of wbicli tliose situated 

 along the ridge of the back are suddenly dilated near the free 

 end (17, 18, 19). The substance of these spines appears to 

 be carbonate of line, as it dissolves rapidly, developing gas, 

 on the application of acid. The grooved spines are filled 

 with a granular substance. The muscular coat, which in the 

 larger specimens attains a thickness of about 1 mm., is remark- 

 able for its abundance of connective tissue. This consists of 

 a homogeneous substance (22 a), in which are found scattered 

 cells, some smaller (0,008 mm.), provided with ramifications 

 (22 b, 24, 25), some considerably larger (0,o2 5 mm.), oblong 

 and without any ramifications (22 c, 26). These last-mentioned 

 cells contain a granular yelloAvish matter, and are provided 

 with a strongly refracting nuclear body. Besides these 

 two kinds of cells, I have in two sections observed other 

 rounded cells, somewhat smaller than the last-uamed, but with 

 conspicuous nuclei and colourless contents (27). 



In this connective tissue muscle- and nerve-fibres are im- 

 bedded, and a great nnmber of ramified canals. The muscular 

 fibres (22 d) are linear and more or less flattened. I have 

 not been able to see any distinct nuclei in them. Viewed 

 edgewise, they present a narrow strongly refracting stripe, 

 whereas viewed sidewise, they appear longitudinally striped. 

 In the inner part of the muscular coat the muscles are much 

 more numerous than in the outer part, and lie close to each 

 other, forming actual strata or bands. Innermost is a layer 

 of ring-muscles of but trifling thickness, after which come lou- 

 gitudinal threads, which are most numerous in the under parts 

 of the body, where they form broad contiguous bands (7 a). 

 These bands decrease in strength upwards, till on the upper 

 parts of the body they almost disappear. Outside them comes 

 another pretty thick layer of ring-muscles, from which issvie 

 a number of threads obliquely outwards, towards the surface 

 of the body. Outside this external layer of ring-muscles, the 

 threads become less numerous, while the connective tissue in- 

 creases in quantity. Most of these threads run in a longitu- 



