10 THOS. H. MONTGOMERY, 



eingebettet werden auch Nervenfibrillen aus ihrem ursprünglichen 

 Lager auf der äussern Ringmuskelschicht mit fort an das Epithel ge- 

 führt." I have found no evidence that these fibres contract spirally, 

 as maintained by Hubrecht ('87). Distally, at the apex of a ridge 

 of the basement membrane, the radial fibres of a cluster fuse to- 

 gether to form a deeply staining mass; proximally they curve out- 

 ward, diverging from one another, so that their proximal portions run 

 parallel to the basement membrane, placed either in the latter, or 

 penetrating between the muscle fibres of the outer circular muscle 

 layer. The ends of the radial fibres do not terminate in cells; but 

 about the middle of each cluster of fibres are frequently found one 

 or two cells, which cells undoubtedly produce the fibres in question, 

 since the radial fibres are structurally equivalent to the other fibres, 

 found in this tissue. The outer layer of the basement membrane 

 stains deepest; this is due to the fact, that the fibres are arranged 

 more densely, and concentrically on the outer surface, while more 

 internally fewer fibres occur (i. e. there is here a proportionately 

 greater amount of intercellular substance), and are not arranged con- 

 centrically, but intersect one another. The outermost portion of the 

 basement membrane is the most deeply staining, since here the fibres 

 are fused together, and the intercellular substance wholly absent 

 Occasional oval, lightly staining nuclei are found in the basement 

 membrane, especially near its inner surface ; and, as Bürger ('90) 

 suggests, these probably belong to intracapsular connective tissue cells, 

 accompanying peripheral nerve fibres. 



In the basement membrane this tissue reaches its greatest dif- 

 ferentiation — the production of special radial and concentric fibre 

 layers; in the remaining portions of the body where it is present, 

 such fibre clusters are absent, and the intercellular substance occurs 

 in proportionately much greater amount. Thus, only when we ex- 

 clude the basement membrane does this tissue deserve the term 

 used by Hubrecht, "gelatinous tissue." The largest cells of this 

 tissue are found between the fibres of the inner circular muscle 

 layer. 



Posteriorly the intermuscular connective tissue is more easily 

 studied than anteriorly, since there the spaces between the muscle 

 bundles are larger, owing to the smaller diameter of the individual 

 muscle fibres. As BIJrger ('90) has first shown, later corroborated 

 by me ('95 a), each non-striated muscle fibre is equivalent to a muscle 

 cell; in the Proto- and Heteronemertini, much more plainly than in 



