180 ZOOPHYTES. 



fifteen deeply muricate tentacula, on maturity. Two, three, four, or five 

 cells were developed successively on some specimens. None acquired a 

 greater number. — Figs, 16, 17, 18, 19, enlarged ; also fig. 27, which is little 

 larger than life. 



In another course of observations, many short spines were rising from 

 the yellow spots, in five days after the prolific vesicles had been set apart ; 

 and in two more days their nascent Sertularise had two, three, even indi- 

 cations of a fourth cell, all yellow. Thus they had attained such maturity 

 in eight days. 



The period is very irregular, for the yellow spots have appeared as 

 suddenly as 24 hours from the escape of the planulse ; also, on one occa- 

 sion, above 40 yellow spots were distributed throughout a vessel within 72 

 hours, during which interval 60 active planula3 had quitted the vesicles. 



Prolific specimens having been lodged in a vessel on April 30, pla- 

 nulse appeared on May 4, and spots next day. Another portion of the 

 same collection of specimens was set apart on May 7. Nothing could 

 exceed their fertility ; they were laden with fine bright yellow vesicles, 

 which discharged their planulse under the observer's eye. In 24 hours, at 

 least 20 circular yellow spots could be seen at the bottom, while many 

 yellow planulse, some of them double the size of their fellows, were in mo- 

 tion. On May 13, not fewer than 70 animals, of various dimensions, and 

 in various states of incipient metamorphosis, all vivid yellow, appeared at 

 the bottom of the vessel — almost the whole vesicles then being empty. 



Thus the nascent Sertularise originate speedily, for they become firmly 

 rooted within 24 hours of quitting the matrix. 



Such changes as now described are great and striking. The motioji 

 of the vigorous planula in all directions is swift, though it is not swimming ; 

 the diffusing root, rising spine and unfolding hydra, look, as it were, the 

 conversion of an animal to a vegetable product. 



Yellow vesicles having been set apart, hundreds of planulse soon after 

 strewed the bottom of a vessel on the 25th of April, rendering every 

 part of it quite yellow. Very few continued in motion two days later. 

 Some were much contracted, others nearly circular. The water being re- 

 newed, all were transferred to a different vessel. Numbers now began to 



