28 Edward T. Browne. [No. 4 



external appearance to be upon the radial canals, as described and 

 figured by Haeckel. 



After dissecting some specimens and cutting a series of trans- 

 verse sections I found that the radial canals were isolated from the 

 gonads and that they proceeded right up to the top of the sub-umbrella 

 and there entered the stomach (Plate IV, fig. 1). A thick layer of 

 circular muscles lines the whole of the sub-umbrella, from top to 

 bottom, and the radial canals run under this layer of muscles. The 

 gonads are upon eight lateral pouches or lobes of the stomach 

 which are suspended by mesen tenes from the wall of the sub- 

 umbrella. The gonads are upon both sides of each lobe and occupy 

 a deiinite position. The wall of the stomach between the lobes is 

 free from gonads, and along the centre of each lobe runs the me- 

 sentery completely separating the gonacl on one side of the lobe 

 from that on the other side, so that there are sixteen isolated go- 

 nads. Their maximum development is on the outer part of the lobes, 

 away from the central stomach. (Pl. IV, fig. 2.) The base of the 

 stomach has the appearance of a small eight-rayed star, formed by 

 the walls of the lobes, and from the corners of the lobes the eight 

 radial canals leave the stomach. Sections show that the gonads do 

 not extend up to the very base of the lobes, so that where the 

 canals leave the stomach there are no gonads. It is clear that the 

 gonads must derive their nourishment direct from the stomach and 

 not by means of the radial canals. 



One of the specimens has its mouth widely expanded allowing 

 a good view of the interior of the stomach. Conspicously situated 

 are eight ridges, running nearly the whole length of the stomach, 

 one between every two lobes. These ridges caught Allman's atten- 

 tion and his figure shows them very well. In his description he 

 calls special attention to the ridges which he called „folds" ; „the 

 folds, with their thickened, convoluted, and gland-like margin, which 

 run longitudinally along the inner surface of the manubrium, con- 

 stitute a very exceptional and striking character." The generic 

 name, "Ptychogastria", is based upon these folds. Sections show 

 that these ridges are formed of a mass of large endoderm cells, a 

 continuation of the wall of the stomach. The preservation does not 

 permit any conclusions to be drawn as to the function of the cells. 



There are probably sixteen marginal sense-organs, two in each 

 octant, situated on the inner side of the margin of the umbrella, 



