L U C E R N A R I ^ A N D T H E I R A T. I. T E S . 67 



instead of at the end, b) drawing tlic edges and ends of tlio digitnlus together 

 toward one side, so as to inclose a hollow space. The genital saccnles {figs. 54, 61, 

 62, 74-77, 98, s, .s\ /) are permanent embodiments of this configuration, but car- 

 ried to a much higher degree of development. They are, in the strictest sense, 

 JioUoto spheroidal saccules, and not mere solid globular masses of tissue and repro- 

 ductive material, and are attached by a sliort, thick neck to the inner face of the 

 circumoral parietes {fi(j. 54, ^). They are totally disconnected from each other, 

 but usually are so crowded that their peripheries come in contact and mutually 

 mould themselves into polygonal shapes. On this account their appearance, from 

 the exterior {fig. 37), is like a mosaic pavement. The oldest are considerably 

 larger than the globular ti[)s of the tentacles. * In a full grown saccule the middle 

 third of the diameter is a spherical chamber (s'), which has its exit through an 

 aperture (s") in the side of the neck. This aperture is as singularly marked in its 

 position as the saccule is in general conformation, for it invariably faces away from 

 the nearest umbellar partition in the direction of the older side of a genital half, 

 and obliquely towards tlie proboscis. We are reminded here of the singular posi- 

 ^tion of tlie liattened sides of the dtglfuU {fig. 98, A, B), which we have taken note 

 of in a former paragraph (117), seeming to sliow a relationsliip something more 

 real than that of mere proximity. The component elements of the walls are also 

 disposed very much after the manner of those of dlglUdl. There is one-half, the 

 exterior {fi,g. 74, i'), of a saccule covered by vibratile cilia, but there are no nemato- 

 cysts, and the other or inner side, instead of coUetocysts (208, A), bears a bed of 

 eggs {fig. 74, g), or spermatozoa {figs. 75, 76), sunken in pouches {s^) formed by 

 folds of the lining wall. Between these two walls the fibrillar of the chondromyo- 

 phtx {If) trend perpendicularly to its surfaces, but terminate against an underlying 

 muscular stratum. There is from one hundred and thirty to one hundred and fifty 

 saccules in each triangular genital half. 



136. The Walls ami Layers have very little to distinguish them in their cellular 

 constituents, or other histological elements, from those cf the circumoral parietes, 

 to wbich the saccules are attached ; but they differ widely in tlunr conformation, 

 and in the substances which they inclose. The outer wall {ouphragma, i') is a 

 direct continuation of the gastrophragma (/), and has the same general characters, 

 cellular composition, and covering of vibratile cilia as the latter, and is spread over 

 the surface of the saccule quite uniformly and smoothly. At the month (s*^) of the 

 saccule a rapid change takes place in the ouphragma, not only in its disposition but 

 also in its cellular structure. Regarding the latter feature first, we will state that 

 the cells {fig. 78, j ) of the interior wall lose the prismatic shape of those of the 

 exterior, and become more or less irregularly oval and flattened, but still retain their 

 relative position in a single layer, although overlapping each other more or less. 



137. The Egg-Follicles of the Saccules. — As- for the lining wall {figs. 74, 77, i') 

 in its totality, it is so disposed about the central chambers C.s') as to render it one 

 of the most conspicuous and important elements among the several peculiar differ- 

 entiations which distinguish the Lucernaritc from all other orders of Acalepha>. It 

 is 2>ar excellence the egg-bearing layer, oophragma, since it immediately incloses the 

 reproductive material in special pouches {s^) wliich arc forn:)t?d by an inversion of 



