20 



PUPATION OF JELLYFISHES. 



which did not itself contract, and yet transmitted the impulse which 

 produced contraction in muscular tissue attached to it, and there 

 appear to be no muscular elements in the newly regenerated tissue, 

 although these often develop later. In these examinations I made 

 use of intra vitem methylene blue, Retterer's method, Flemming's 

 fluid followed by Ehrlick's acid hematoxylin, corrosive sublimate 

 followed by aqueous carmine stain, and Hermann's fluid, but in no 

 case could I find muscular elements in sections of the newly regener- 

 ated tissue which appeared to be a simple columnar epithelium, under- 

 laid by a thin nervous net- work (see fig. 36). The muscle fibrillse 

 of the sub-umbrella are striate, and are easily demonstrated by any of 

 the above methods.* 



A B 



act ect cct C 



m, 



Figs. A-C. Cross-sections of the sub-umbrella of Cassiopea. 

 Fig. D. Surface view of newly regenerated sub-umbrella 

 tissue, ect, ectodermal epithelium. Q, gelatinous substance of 

 the disk. M, muscle fibers. 5, basal membrane. 



Figure A is a cross-section of the normal uninjured sub-umbrella of 

 Cassiopea, cut across the trend of the circular muscle fibers ; while fig- 

 ure B is a cross-section through regenerated sub-umbrella epithelium 

 which has grown over an area from which all cellular elements had 

 been cut away about 40 hours before. This newly regenerated tissue 

 can not itself contract for, as yet, it lacks muscular elements ; but it 

 will nevertheless transmit the stimulus which produces contraction in 



*Hesse (1895) finds that the nerve fibers in the sub-umbrella of Rhizostoma pulmo 

 extend in all directions, but are mainly grouped in clusters extending from sense- 

 organ to sense-organ. Bethe (1903) finds that in Rhizostoma and Cotylorhiza the 

 epithelium of the sub-umbrella is connected with the deep-lying muscles by means of 

 an intermediate plexus of nerve fibers. 



