168 BULLETIN OF THE 



Internal changes, in addition to those already mentioned, accompany the de- 

 velopment of the ephyra into this stage of the young Cijanea. The stomach 

 cavity is prolonged into extension between the umbrella and the lower floor of 

 the medusa, as in the youngest ephyra, but these extensions have become 

 broader, as the lobes in which they lie have become widened. The lateral 

 branches, which in the ephyra were almost tubelike, are now much broader, 

 yet still without bifurcations at their extremities. The circular muscular folds 

 have become more clearly differentiated, and on the under side of the walls of 

 the young medusa triangular-shaped muscles connected with these cu'cular folds 

 have begun to push out into the sense octants. In each sense octant there 

 is a pair of these muscles, which at this stage are very minute, but are later 

 greatly developed in the " under floor " of the adult. The otocyst of younger 

 stages, as well as of the ephyra, is simpler than that of the adult. The " hood," 

 which in the adult (d, Plate VII. fig. 12') covers and protects the sense organ, is 

 not developed in any of the ephyra-like stages. The same is true of the oral 

 curtains, Plate VII. fig. 12, c, which hang down on either side of the otocyst in 

 the adult. 



One half of an octant of a young Cyanea still older than that represented in 

 Plate VII. fig. 8 is sho^vn in Fig. 7. The more important internal changes which 

 have taken place are the results of the enlargement and filling out of the margin 

 of the umbrella to a more regular and unbroken outline, and the addition of new 

 tentacles in the marginal clusters. There is also a multiplication of sexual fila- 

 ments, many of which have been removed from the figure to avoid complication. 

 The function of these sexual filaments in the adult is somewhat doubtful. 

 They are said to have a motion by which the water in proximity to the sexual 

 organs is removed, and pure water continually made to replace the impure. 

 This motion I have never observed, nor am I able to distinguish the male 

 Cyanea from the female. The figures which are given in Agassiz's " Contribu- 

 tions " of the immature ovaries and spermaries, resemble each other very closely, 

 the spermaries possessing folds in the mesentery-like membrane (o. s.). Are 

 not like folds also sometimes found in the ovarian organs? I figure, Plate 



VII. fig. 13, the ovaries of a Cyanea, of which the ova were not mature. Plate 



VIII. fig. 13, illustrates the microscopical structure of the egg and its envelope 

 in the ovary of the same age. 



Outside the four tentacles formed in the re-entering angles of the lips of the 

 ephyra of Cyanea, there is a ring in the lower floor which is less transparent 

 than the remainder of the floor, and thickly striated. This ring is the origin 

 of the muscular folds in the lower floor of the adult Cyanea. The lower floor 

 is joined to the umbrella itself by perpendicular partitions, eight in number, 

 each situated on the lines where the sense octants join each other. 



In the angle of the incisions in the margin of the umbrella separating the 

 lobes which bear the otocysts, there arises from the oral side of the e])hyra, at 

 the same time with the sexual tentacle, another of about the same size. As 

 there are eight of these incisions, there are at first eight of these tentacles. 

 They originate as simple buds, and elongate to a length equal to the diameter 



