76 THE INDIVIDUALITY OF 



which the reproductive organs are situated were to be separated 

 from the body and left to take care of itself, we would have pre- 



trace them in the knotted forms. In course of time the eggs (6*7) are metamor- 

 phosed into the secondary or planula stage, and the young in this condition, re- 

 sembling opaque orange-colored globules, escape from the sac in which they 

 originated. At the time, in May, when I discovered this peculiar form of repro- 

 duction, the egg-sacs (II), of a club-shaped figure, were comparatively much 

 smaller and far less conspicuous than the knotted form (III, IV), and conse- 

 quently the latter attracted my attention first. Most prominent among these 

 were those represented in No. Ill of this group, and at first they were mistaken for 

 the feeders which had lost their feelers, and whose meduso-genitals were crowded 

 all over the head. Presently, however, a more expanded form (IV) was met 

 with, which had one (pfi) of the young still within the space between the outer 

 wall (o 2 ) and the proboscis (pr 2 ), and the latter was partially coiled around it. 

 This revealed the character of the knotted heads, for it had also on its outside 

 the globular planulae (p l ) which gave it the irregular outline that first attracted 

 my attention. Returning then to the tallest and most slender of them (III), 

 I found some in which, although the outer (o 1 ) and inner (/;>') walls were nearly 

 as closely approximated as in the sterile hydra, there was yet one young planula 

 left (pl l ) ; and in addition, to clear up the mystery, the fissures (op) in the outer 

 wall, through which the young escaped, were quite conspicuous at two or three 

 points. 



Why, then, were the slender forms mistaken for feeders which had lost their 

 feelers, and why did they seem to be covered with nieduso-genitalia ? Simply 

 because that when the planules escape through the fissures (op) of the meduso- 

 genital, they are kept from dropping away from it by the thin, filmy envelope 

 (jt>, J5 1 ), which, it appears, has a great degree of ductility ; and very naturally, from 

 their position, the planules appeared to be groups of closely set reproductive sacs, 

 i. e. meduso-genitalia, with exceedingly short stems for attachment to what ap- 

 peared to be the head of the hydra. The whole process of this affair may then 

 be summed up thus : the eggs maturing and changing into planules, the latter 

 escape in succession through the outer wall of the sac ; and as this goes on, the 

 sac shrinks and approximates the inner wall (III, pr), until, when all the 

 planules are expelled, the two walls (o 1 , pr) lie close together, apparently as in 

 the sterile hydra, and thus this meduso-genital appears to have all the characters 

 of the latter, excepting its feelers. 



What is the subsequent fate of the fertile form, I have not been so fortunate 

 as to ascertain; nor has any observer taken note of it; although it has been 

 assumed, and in fact positively asserted, that it finally becomes " metamorphosed 

 into a hydra." (See in Agassiz's " Contributions," vol. iv. p. 226, the editor's 

 totally unwarrantable assertion, intercalated in italics between my sentences, in 



