210 HYATT, 



buds developed from the original, or parent cell of the 

 colony. 



Besides these, however, there are other characteristics, 

 such as the decrease in the tenacity with which the endo- 

 cyst adheres to the ectocyst, finally resulting in its ability 

 to glide easily over the surface of the latter in Cristatella, 

 the decrease in the pergameneous nature and permanency 

 of the ectocyst, all traceable to the increase in the soft- 

 ness and gelatinous nature of the ectocyst. And still 

 following in the same category we find that the decrease 

 in the number of branches to each colony, the great in- 

 crement in the thickness of the ectocyst in Pectinatella, 

 and the disappearance of the permanent annular folds, is 

 due to the greater functional activity of the third layer 

 in forming annular folds, traceable in turn to the increase 

 in the gelatinous nature of the ectocyst, which permits 

 these folds to coalesce and divide the colonies. Thus, 

 there are two series of important structural character- 

 istics, which necessarily change in consonance with, or 

 are dependent upon the gradual change of the parchment- 

 like ectocyst of Fredericella, to the gelatinous, transient 

 excretion of Cristatella. 



This gelatinous condition of the ectocyst, as has been 

 shown, is only a rare individual characteristic in, Freder- 

 icella, becoming peculiar to some species in Plumatella, 

 and, finally, essential to the organization of Pectinatella, 

 Cristatella, and perhaps Lophopus. I have succeeded in 

 producing the transparent, gelatinous ectocyst in Freder- 

 icella, by simply allowing a colony to grow in Avater free 

 from all sediment ; and I have not yet found a transparent 

 variety or species except in clear water. The trans- 

 parent ectocyst is also common in the young of all the 

 brown varieties of Fredericella and Plumatella, and these 

 are much longer lived than the transparent species, such 

 as Plumatella vitrea, the Pectinatellee or Cristatella}. 

 Whether the ectocysts of P. vitrea would become brown 

 and tougher if they lived longer, it is impossible to say ; 

 but certainly such would appear to be the most likely 

 result, since the ectocyst of all the brown Fredericellae 

 and Plumatellse, which live longer than they do, are trans- 



