260 SIDNEY F. HARMER. 



before the loss of the calyx ; and, in the second place, that the 

 tissues have already acquired, at the metamorphosis, the power 

 of disposing of degenerated structures. 



In the Ectoprocta one may hence suppose that, owing 

 to the inconvenience of losing a portion of the zooecium at each 

 rejuvenescence, the new polypide is budded oflF near the pre- 

 ceding one, instead of from an entirely diflFerent part of the 

 zooecium, as in Pedicellina (below the diaphragm). The 

 degenerating alimentary canal and other structures are then 

 worked up by the '' Parenchymgewebe" (Vigelius), which has 

 inherited this kind of power from the larval tissues, into the 

 condition of a " brown body," which passes into the new 

 stomach, and reaches the exterior by means of the anus. 



In the development of the Ectoprocta an archenteron is 

 formed, in a large number of cases at least. The embryo is, 

 however, richly supplied with yolk ; it develops within the in- 

 terior of the parent, and its alimentary canal is hence, in many 

 cases, functionless. 



At its metamorphosis this larva possesses no functional ali- 

 mentary canal, and must hence form a new one. But since in 

 its previous phylogenetic history our Polyzoon has acquired 

 the power of developing new " polypides" from various parts 

 of its ectoderm, a fresh gut could without difficulty be formed 

 within the body wall of the metamorphosed larva ; since the 

 latter is now in the same condition as an adult zooecium whose 

 polypide has just become a " brown body.'' 



This, indeed, is what actually happens. The larva passes at 

 once into the condition of a zooecium containing a " brown 

 body," the remains of its larval organs. The complicated me- 

 tamorphosis of Pedicellina has been given up, the larval 

 structures now degenerating by the method employed during 

 the atrophy of the polypides in adult individuals, and finally 

 leaving the zooecium bypassing as the first "brown body" 

 into the alimentary tract of the primary polypide, and thence 

 to the exterior. 



The metamorphosing Ectoproctan larva is probably in 

 the same condition (irrespective of the difference pointed out 



