ON BUDDING IN POLYZOA. 543 



pretation of the similar process in Crista tella. This con- 

 tinually constricting sac described by Hatschek lies between 

 the epiblast and the mesoblast of the stolon, and it is quite 

 open to us to discuss its morphological value. If we look upon 

 this sac as hypoblastic tissue derived from the archenteron of 

 the embryo, the budding of these fresh-water Polyzoa would 

 present no difficulty. Alhnan describes the initiatory steps of 

 the formation of a colony. If we accept a different (i.e. a 

 hypoblastic) origin of the internal epithelium of the alimentary 

 tract of the earliest polypides than that which Allman indicates, 

 then the two accounts mutually assist one another. 



Reinhardt (25) states that in Alcyonella fungosa and 

 Cristatella mucedo: "After segmentation the mass is con- 

 verted into a gastrula by invagination ; the gastrula-mouth 

 closes and the segmentation cavity disappears.^' . 



"The cystid (in Cristatella) consists, as in Alcyonella, 

 of an ectoderm, a median layer (the tunica muscularis), and an 

 entoderm. Thus, Hatsckek must be wrong when he names 

 the inner layer of the bud mesoderm, and his description of 

 the budding is inexplicable by comparison with the above- 

 mentioned details, though these may perhaps correspond with 

 his second unknown process of budding. The bud develops by 

 a thickening of the ectoderm into which the entodermic cells 

 are pushed ; there is no indentation of the former. The 

 tunica-muscularis is very early formed ; the cavity of the 

 tentacle-sheath is separated later from the alimentary canal, 

 and the lophophore is formed by an invagination into this 

 tentacle-sheath. The later development of the buds corre- 

 sponds with that described by Nitsche in Alcyonella." 

 (From the English abstract.) 



Reinhardt clearly gives us the three germinal layers, it is 

 difficult to unflerstand him perfectly as he gives no figures, but, 

 accepting his statements, we apparently have an embryo in 

 which the alimentary canal has a retarded development, an 

 embryo which is, in fact, all body-cavity, such an embryo can 

 easily result from an ordinary enterocoelous form, such as 

 Argiope, Sagitta, &c., by an exaggeration of the coelomic 



