MICKOIIYDRA DURING I907. IO3 



M. ryderi has "saved its face," all three of them, in fact, 

 and seems now as able to " roar after its prey " as ever. I 

 am happy to be able to state that the hydra recovered. 



ONR SINGLE MEDUSA DURING 1907. 



Still another extract from my note book, though of earlier 

 date than that which has been already recorded, seems to have 

 its appropriate place here. I have told what I have seen this 

 year of the life history of Microhydra and its asexual multi- 

 plication by means of larval hydroids. The single opportunity 

 of the year, of witnessing the growth of a true sextial bud 

 and the liberation of a free swimming medusa remains. 



In the Quarterly Jonrnal of Microseopical Science, Volume 

 50, November, 1906, Plate 46, Figures 15 and 16; and in the 

 Proceedings of the Delatvare Couyity Institute of Scie7ice ,^1 o\wxa^ 

 II, Number 2, Figure 5, is shown all that has already been 

 illustrated of the initial stages of these buds. Under date of 

 September i6th, 1897, I find the following remarks, written 

 in my note book apyvpos of the observations that had been 

 made ten days earlier : — 



" Several points remain to be observed — such as the first 

 appearance of the medusoid bud ; its gradual enlargement, 

 including the prolongation of its pedicle ; its condition at the 

 first opening of the distal extremity ; the relation of the first 

 pulsating movement to that opening ; the formation and 

 development of its eight tentacles and its final separation 

 from the hydroid body." It continues: " The distal surface 

 of the unopened bud, at least above the line of the future 

 marginal canal, appears closely covered with thread cells. 

 When first seen, a single tentacle is found at the junction of 

 each radial canal with the marginal canal, and four more at 

 points midwa}^ between these pairs. These eight tentacles 

 appear nearly or quite of equal lengths, and to be developed, 

 not by longitudinal growth or prolongation, but by radial seg- 

 mentation from the surface of the disc. A close examina- 

 tion will, I think, show this distal surface to consist of two 



