24 Prof. H. J. Clark on Lucernaria. 



unlooked-for structure, hitherto unknown among Acalephse. 

 What appear to the naked eye to be eggs of enormous size 

 are really little pouches, which contain either numerous eggs or 

 matrices of spermatic particles, according as the individual is 

 male or female. Each pouch, or genital saccule, as it may be 

 called, projects freely into the digestive cavity, and is attached 

 by a very short and rather narrow neck to the inner wall of the 

 oral floor of the disk. This constitutes another step in the 

 specialization of these organs, but does not complete the process. 

 At the base of each genital saccule, and on that side which faces 

 toward the proboscis, there is a small aperture, which leads to 

 the interior, where there is a considerable cavity. This cavity 

 is formed by the lateral inversion of the single wall of the sac- 

 cule upon itself, and the constriction of the wall about the en- 

 ti'ance to the chamber. The eggs or spermatic material* are 

 enclosed in saccular folds of the wall of this chamber, into 

 which they fall when mature, and pass thence outwardly through 

 the lateral outlet at the base of the saccule. One may see at a 

 glance that this is a type of the reproductive organs not to be 

 found among the other Acalephse. 



In Aurelia the generative products, whether eggs or sperma- 

 tozoa, lie immediately beneath the outer wall, and imbedded in 

 the muscular layer which extends throughout the length and 

 breadth of the oral face of the disk as I have described it in the 

 fourth volume of Professor Agassiz's 'Contributions.' Between 

 the muscular layer and the inner wall which forms the imme- 

 diate parietes of the digestive cavity, a thick layer of gelatini- 

 form substance intervenes ; and its presence naturally suggests 

 the inquiry. How are the eggs or sperm to escape into the di- 

 gestive cavity, as they are known to d(^? The spermatic particles 

 I have observed frequently escaping directly through the outer 

 wall into the ocean; and I have seen them, with the broadest end 

 out, projecting like bundles of hairs from the cavity of the matrix 

 through the apertures in the outer wall. When the reproduc- 

 tive material is fully ripe, the inner wall, with the gelatiniform 

 layer, and the muscular layer as far as it includes the material 



* The spermatic particles have an elongate-cordate body, from the broad 

 end of which an excessively long tail-like filament trails in broad curves as 

 it swims; at the pointed end are attached two exceedingly delicate fila- 

 ments, which are in constant motion, bending and coiling, or stretching in 

 every direction, as if they were the tactile organs of an Euglena or some 

 other similar Infusorian. The pseudoproboscides defy detection with ordi- 

 nary objectives; in fact, to determine their presence with certainty requires 

 very careful manipulation of such objectives as have the most accurate 

 defining-power, and which are to be obtained only from our best makers. 

 The spermatic particles of our common Echinus {E. granulatus) also pos- 

 sess a double pseudoproboscis. 



