8 Prof. M'Intosli's Notes from the 



Nowikoff* (1012), illustrated by representations of stained 

 sections, wliich indicate tlie position of muscles, nerves, and 

 blood-vessels as well as tlie skeletogenous elements. He 

 rc""ards the snp|Hirtinji- substance as lioniologons 'svitli that 

 in Mollusca and \'crtebrates, presenting, moreover, less 

 polvgonal or somewhat rounded cells, with ground-substance 

 of a chondro-mucoid character, with nuclei and ])roto- 

 plasniic contents, and having externally a layer, which he 

 terms perichondrium, upon which the cuticle and its nuclei 

 rest. Tiic author docs not go into the distribution of the 

 skeleton in the foregoing forms, but confines his attention 

 chiefly to the histology of the tissue, the so-called *' carti- 

 lage "-cells being filled wnth fluid, and almost resemble 

 plant-cells from their distinctness. They possess one, rarely 

 two, nuclei. The perichondrium is granular and has an 

 alveolar (basement-) layer between it and the hypodcrm. 



The structure of the body-wall in Sahella peniciUus, L., 

 is typical, though there are special developments of the 

 surface. Thus, on each side of the mid-ventral line a thick 

 glandular layer outside the circular muscular coat occurs. 

 This appears to be a special development beneatli the hypo- 

 derm, which is readily traced over it and along each side of 

 the mid-ventral fissure. The circular musciilar coat is Avell 

 developed and is continuons or nearly so. The dorsal longi- 

 tudinal muscles are in section thick externally, but taper to 

 the mid- dorsal line, where a hiatus for the suspensory 

 mesentery of the alimentary canal occurs. These muscles 

 are comparatively narrow and do not reach the lateral edge. 

 In the same way the ventral longitudinal muscles are compact 

 or almond-shaped in section, slightly thinned internally, and 

 each is separated by a wide gap from the muscle of the 

 opposite side. Both dorsal and ventral longitndmal muscles 

 have a translucent sarcolemma on the free surface and both 

 show bands of sarcolemma here and there cutting the mass 

 into various fasciculi. Under the inner edge of each lies 

 the nerve-trunk surrounded by neuiilemma and with com- 

 paratively little nenroglia. On the upper and inner e([gQ. of 

 each is a large neural canal, which in many sections is larger 

 than the nerve-trunk and is occupied by a coagulable 

 material. It appears to be unnecessary to call such a tube 

 a giant nerve-fibre, and, indeed, the term neural canal was 

 adopted in 1877 f, and luay as well comprehend the finer 



* Zeitsch. f. w. Zool. Bd. ciii. p. 680, Taf. xvi. 



t " On the An-angenient and Kelations of the Great Nerve-cords in 

 the Mari'io Annelids?," Proceed. Koy. Soc. Ediu. Session 187G-77. 



