ON BUDDING IN POLYZOA. 533 



organs, viz. the epiblast, to the external skin, the lophophore, 

 the intra-tentacular space, the cESophagus, rectum, and nervous 

 system ; the hypoblast, to the stomach with its digestive cells, 

 and the intestines; the mesoblast, to the muscles and general 

 parenchyma of the body. The generative organs apparently 

 arise from a special mass of mesoderm cells, which very early 

 appear as a single cell, which may arise from the primitive 

 hypoblast, or may be one of the primitive embryonic mesoderm 

 cells. After describing the embryonic bud, Hatschek says 

 (p. 515): — " The whole formation, which we have just studied, 

 gives, as will be shown further on, the material for the con- 

 struction of all the secondary individuals of the stock, whilst 

 the whole of the remainder of the larva goes directly over to 

 the primary oldest individual." 



It appears that Prof. J. Reid (2) was one of the first (1845) 

 to point out the fact that new buds form on the stems of 

 Pedicellina echinata when the polypides die; it has also 

 been noted by several observers since. It would be a most 

 interesting fact if this process were found to take place when 

 no remnant of the polypide was left. The histology and mor- 

 phology of this phenomenon require to be elucidated. 



EcTOPROCTA — Gym nol^m ata 

 (Marine Polyzoa). 



Nitsche (13) makes a distinction between the outer epithelium 

 of the eudocyst and the inner muscular layer, and he derives the 

 outer epithelium of the lophophore and tentacles and the inner 

 epithelium of the alimentary canal of the bud in Flustra 

 membranacea from the former (" Epithelialschicht ") — in 

 other words, for him, the lophophore and alimentary canal of 

 the young bud have a purely epiblastic origin. The tentacular 

 sheath, the muscles and peritoneal lining, &c., of the polypide 

 being derived from the inner muscular tunic of the eudocyst, 

 i. e. from mesoblastic tissue. 



In Fl. membranacea all the changes in the decadence of 

 a polyp into a brown-body can be seen; this is yet more 

 clearly manifest in Alcyonidium hispidum. Here single 



VOL. XXIII. NEW Stll. N N 



