Dr. Reid on the Development of the Medusse. 37 



numerous minute nuclei disseminated through it. Numerous 

 nearly elliptical and oval capsules (filiferous capsules), having a 

 long thread or filament coiled up in the interior of each, are fixed 

 upon the outer surface of the external layer, and in much smaller 

 number upon the inner surface of the internal layer, where it lines 

 the internal cavity or stomach. These capsules are most abundant 

 upon the external surface of the tentacula. Fig. 20 is a highly en- 

 larged view of a small portion of one of the tentacula, showing 

 the filiferous capsules attached to its outer surface. These fili- 

 ferous capsules vary much in size, but the largest are generally of a 

 uniform size, nearly of an elliptical form, and about 2 oV o^^^ ^^ ^^ 

 inch in their largest diameter (PL V. fig. 8). Several of these, de- 

 tached in examining portions of the larva under the microscope, 

 had burst open at the smaller end, and the spiral thread projected 

 through the opening and was imcoiled (fig. 9). In the entire 

 capsule a rounded and narrow column passes from the smaller end, 

 beyond which it slightly projects, in the direction of its longest 

 diameter, nearly to its other extremity ; and this column, to which 

 the spiral thread is attached, protrudes from the interior of the 

 capsule when it bursts. I have never observed these filaments 

 projecting from the capsules when adhering to the surface of the 

 body, unless when subjected to pressure, but it is difficult to use the 

 more powerful object-glasses necessary for distinguishing these, 

 without compressing more or less the part under examination. 



The internal is considerably thicker and more opake than the 

 external layer, is of a slightly yellowish colour when it accumu- 

 lates at any point in greater abundance than usual, and is folded 

 inwards to form the four equidistant projections seen on the sur- 

 face of the stomach when the mouth is dilated (fig. 5 a), and 

 when the body of the animal is slit open and then spread out 

 (fig. 6 c). By making a transverse section of the body, the rela- 

 tive thickness of the internal and external layers, and the man- 

 ner in which the internal is folded to form the four pouches or 

 short canals that project from the internal surface, are very di- 

 stinctly seen (fig. 7). These four short canals (fig. 7 a) termi- 

 nate at their upper end in another canal, encircling the mouth 

 and placed between it and the margin of the disc (fig. 6 A). Into 

 this circular canal the hollow tentacula also open. The inner 

 surface of the cii'cular canal and the tentacula is lined by the in- 

 ternal layer. The four depressions (fig. 2 a) placed between the 

 mouth and margin of the disc correspond to the termination of 

 the four vertical in the circular canal. Across the bottom of 

 these depressions, which at first sight look like apertures, a mem- 

 brane is stretched sufficiently thin to permit readily of the trans- 

 udation of fluids. 



After reading Steenstrup's observations on the structure of 



