164 SIDNEY F. HARMBR. 



It appears to me probable that the growing point of the 

 stolon of Pedicellina {vide fig. 13) consists solely of an ecto- 

 dermic layer secreting a cuticle and of a mass of indiflFereut 

 mesodermic connective-tissue cells, embedded in a structure- 

 less jelly. If this is the case, the only organ derived from the 

 hypoblast of the embryo would appear to be the mesenteron of 

 the primary individual, all other parts of the colony being 

 devoid of any derivatives of hypoblast cells. 



This conclusion can hardly be avoided unless we assume that 

 some of the stellate cells of fig. 16 are really hypoblastic in 

 nature, although indistinguishable from the mesoderm cells in 

 their appearance. Owing to the nature of the process by 

 which the dorsal organ degenerates, it is impossible to assert 

 that some of its cells do not become amoeboid wandering cells 

 which migrate into the growing point. It can, however, be 

 safely stated that no hypoblastic vesicle is formed from the 

 degenerating dorsal organ. It may further be pointed out that 

 the conclusion arrived at on a previous occasion as to the 

 nervous (epiblastic) nature of the dorsal organ, in Pedicellina 

 as in Loxosoma, is in opposition to the view that this struc- 

 ture plays any part in the budding. 



The well-known fact that calyces of Pedicellina may fall 

 from their stalks, which thereupon develop new calyces, appears 

 to me in direct contradiction to Hatschek's view of the bud- 

 ding. The loss of the calyces is probably a normal, periodically 

 occurring process, which is perhaps to be regarded as a means 

 of rejuvenescence^ and which is at least analogous to the forma- 

 tion of the " brown bodies " in the E c t o p r o c ta. It is exceed- 

 ingly easy to discover individuals in healthy colonies in which 

 the calyx has been lost, and a new " bud " (easily recognised 

 by its small size and immature condition) is being developed 

 just below the scar. Specimens kept in captivity seem inva- 

 riably to lose their calyces if the quantity of water is not very 

 large, the calyx falling off at the "diaphragm." This struc- 

 ture, which is merely a constriction at the base of the calyx, 

 filled by a row of flat cells, is perhaps a special arrangement 

 by which the calyx can break away from the stalk, without 



