50 



the partition, and extend along the inner face of the oral floor of 

 the disc fi-om the base of the proboscis to the extreme limits of the 

 corners of the disc, where they almost touch the bases of the tenta- 

 cles. Across the proximal end of each partition, triple or quadruple 

 rows of slender digltiform bodies extend each way for a considerable 

 distance along the border of each half of a genital, thus forming the 

 common appendages of the two, and clearly indicating their unity. 

 Each half has a peculiar form, which may be represented by an ine- 

 quilateral triangle whose longest side extends nearly in a straight line 

 from the inner end of the partition to the tentacles, and the two other 

 sides, slightly curving outwardly and meeting at a very broad angle, 

 form the rest of the outline. In the adult, the longest side of the 

 triangle is to its height as two to one. This feature, alone, has a de- 

 gree of speciality which raises these organs in rank above all others 

 of their kind among Acalephse ; but when we examine their compo- 

 nents, we find an unlooked-for structure, hitherto unknown among 

 Acalephte. 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 disc. 

 This constitutes another step in the specialization of these organs, 

 but does not complete the process. At the base of each genital sac- 

 cule, and on that side which faces toward the proboscis, there Is a 

 small aperture, which leads to the Interior, where there is a consider- 

 able cavity. This cavity is formed by the lateral Inversion of the 

 single wall of the saccule upon Itself, and the constriction of the wall 

 about the entrance to the chamber. The eggs or spermatic mate- 

 rial are enclosed in saccular folds of the wall of this chamber, and 

 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 Acalephag. 



In Aurelia, the generative products, whether eggs or spermatozoa, 

 lie immediately beneath the outer ivall, and imbedded In the muscu-- 

 lar layer which extends throughout the length and breadth of the 

 oral face of the disc, 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 Immediate parietes of the diges- 

 tive cavity, a thick layer of gelatinlform substance intervenes, and 

 its presence naturally suggests the Inquiry, how are the eggs or 

 sperm to escape into the digestive cavity, as they are known to do ? 

 The spermatic particles I have observed frequently escaping directly 



