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PROCEEDINGS OF THE 



[Dec, 1856. 



for, on one occasion, when ova were expelled by artificial com- 

 pression, they were only found immediately near the opening of 

 the mouth. 



I am, consequently, also, as yet, ignorant of the form of the 

 genital product at the time of expulsion. On one occasion I ob- 

 served, in the upper part of the disk cavity of a large specimen r 

 several opaque spherical ova resembling those I had, on a previous- 

 occasion, forced out by compression, and which were entirely 

 without either proboscidian elongation or indications of tentacula — 

 unfortunately, I was compelled to leave the observation at that 

 moment, and have never had a recurrence of the phenomenon;- 

 But the specimen m which this was observed was not in a healthy 

 condition, and it is not at all unlikely that the expulsion may have 

 been premature and abnormal. 



If, however, this be the real condition of the young when born, 

 we will have here a state of things like that in some Tubularioe, 

 where the young passes as a globular planule into the bell concave 

 between the proboscis and wall of the cavity, and there remains 

 until the tentacula are developed. But while this easily takes 

 place in such fixed Medusae, as deriving their nourishment through 

 Hydra mouths, can keep the vailed rim of the bell closed, it is dif- 

 ficult to conceive how, in the swimming Turritopsis, the globular 

 germs could be kept from expulsion into the water at any pulsa- 

 tion of the parent's disk. It is, however, possible from the pe- 

 culiar shape of the disk, that the contents of the upper portion of 

 the sub-umbrella do not receive the downward impulse given by 

 the contraction of the bell. In that case, the embryo noticed 

 above may have been even kept in position by the parent's pul- 

 sations. 



Still further, in regard to this stage of the development, the most 

 imperfect form of larva which has yet fallen into my hands, was 

 one of which I give two much magnified outlines, PI. 6, fig. 19„ 

 It was proboscidian, and apparently unprovided with tentacula. I 

 suppose during the present summer I have seen very little fewer,, 

 if not more, tha>n an hundred larvse, but among all these this was 

 the only untentaculated specimen, not the product of gemmation, 

 which fell under my observation. It was clinging to the tentacu- 

 liferous border of the parent's disk, by means of the extremity of 

 its own proboscis. This circumstance also was peculiar, since in 

 no other instance have I seen the larva to use the proboscis as 

 even a means of temporary adherence for the purpose of Jocomo- 



