MUSEUM OF COMPAEATIVE ZOOLOGY. 263 



The mouth of the ephyra is simple, quadrate, and there is a single gastral 

 filament in each quadrant. The lips are simple raised ridges from the lower 

 floor of the stomach, and assume a cruciform outline when seen from beneath. 

 The chymiferous tubes are broad extensions from the stomach to the tentacles 

 and otocysts. No extensions of the central cavity as yet push out towards the 

 marginal lobes. 



In an ephyra still older than that just described, we have anatomical differ- 

 ences of a most important kind. While the general outline, color, and pigmen- 

 tation is about the same as in the former, important additions have taken place 

 in the internal anatomy. Prominent among these is the formation near the 

 base of each tentacle of a spherical body filled with cells. These bodies are 

 seen in fig. 3. They are the beginnings of the ovaries which in later stages 

 assume a different form, and by coalescence form the horseshoe sexual glands 

 of the adult. Intermediate between the broad prolongations from the stomach 

 cavity, which in the young ephyra extend to otocyst and tentacle, smaller 

 blindly ending tubes push out in the direction of the marginal lobes. They 

 are as yet very short, hardly entering more than the base of the lobe. 



By far the most interesting anatomical structure in this as well as subsequent 

 stages of the ephyra is the differentiation of the stomach cavity into an upper 

 and lower story, by the growth of a continuation of the lower floor of the bell 

 into a partition in this structure. In an ephyra as young as fig. 3, this differ- 

 entiation has been accomplished, and the only communication between the 

 stomach proper and the chymiferous cavity above is through a centrally placed 

 opening in the lower floor. 



The number of gastral filaments in each cluster has very much increased, 

 and their ends often project through the central orifice in the wall which 

 divides the stomach from the chymiferous cavity, just as also happens in the 

 adult Linerges. 



In the oldest ephyra (fig. 15) the approximation in shape and color to the 

 adult Linerges has gone still further. The depth of the incisions which sepa- 

 rate the marginal lobes has diminished, and the bell has become more thimble- 

 shaped, the apex rising and the walls becoming more vertical instead of 

 horizontal. The circular muscles in the lower floor have also clearly differen- 

 tiated themselves from the inner wall of the bell. 



One of the most important changes which has taken place is in the form of 

 the eight ovaries. As the spherical glands of the ephyra (fig. 3) grow in size 

 with the development of the larva, two bulges form on adjoining sides near 

 the ends, and gradually approach each other. As growth goes on, these pro- 

 jecting portions join, and we have the eight glands fused into four, each 

 assuming a crescentic shape, as in the adult Linerges. The mode of growth 

 of the ovaries has been one of the strongest facts pointing to the relationship 

 of the ephyra to Linerges. 



