HYDROIDS FROM WOOD's HOLL, MASS. 349 



evident that it was not the plaimla of a hydroid), and developed 

 into a young Hypolytus, thus settling the question beyond a 

 doubt. 



As the segments freed from the foot end of Hypolytus are 

 destined to form new polyps directly, and differ from any kind 

 of bud heretofore described, as will be shown later, I shall 

 call them blastolytes. 



From a large number of cases of asexual reproduction ob- 

 served, the following record of the typical course of events is 

 made. 



The first signs of the process are seen in the deeper hue 

 taken on by the free end of the polyp, which is no doubt due 

 to the concentration of material for future use. A slight 

 thickening also takes place at this time, and both these phe- 

 nomena may be due to a very slow mass-contraction at the 

 foot end, or they may be due to constructive metabolism. 

 This point is an important one, but must be deferred until 

 microscopic examination of tissues is made. Next a constric- 

 tion is seen about two and a half times its diameter from 

 the foot end (fig. 2, h). The fact that it forms very gradually 

 and without any marked contraction of the body at this point 

 warrants the conclusion that this and the subsequent process 

 of complete fission are purely cellular activities. Frequently 

 before the first blastolyte is entirely constricted off a second 

 circular groove marks off another blastolyte (fig. 2, a) ; and 

 even a third has been seen in close succession to the other two 

 but not more than two have been observed at one time. 



Just as soon as one blastolyte is freed, its oral end (its 

 polarity, judging from all my observations, remains the same 

 as that of the parent) becomes rounded and somewhat thicker 

 while the aboral is drawn out to be more slender, — probably a 

 shifting of material to a point where it will be soon needed for 

 the rapid development of the two sets of tentacles, the first 

 necessary organs for securing food. 



From the usually curved position of the foot, as indicated in 

 the anatomical portion, the blastolyte lies almost horizontal or 

 at most somewhat inclined. From this position it rises up as 



