28 JOHNS HOPKINS UNIVEESITY MORPHOLOGICAL MONOGRAPHS. 



hands, and so far as the vascular lamellae are concerned my own work is 

 only a confirmation and amplification of his, since Charybdea and 

 Tripedalia in this respect agree with Chiropsalmus. 



The vascular lamellae of the internal system are the most prominent 

 and morphologically the most important. They comprise the four 

 vertical strips of fusion that separate the four stomach pockets in the 

 interradii (ivl in the figures of the series of cross-sections of Charybdea 

 and Tripedalia, Nos. 6-15 and 21-29), and four curved horizontal cross- 

 pieces at the top of these which separate the stomach from the stomach 

 pockets, and would make the separation complete did they not leave in 

 each perradius a free space between their ends, which makes possible the 

 gastric ostia. 



The arrangement of this internal system of vascular lamellae is 

 simple. What they amount to is a certain definite number of linear 

 adhesions between the two walls of an originally undivided gastro- 

 vascular space, by which that space is divided up into a central stomach 

 and a peripheral portion, and the peripheral portion thus further divided 

 into the four stomach pockets. Perhaps the idea may be conveyed by 

 likening the whole medusa to a couple of bowls fitting closely one within 

 another and plastered together at the margins. The exumbrella then 

 would correspond to the outer bowl, the subumbrella to the smaller inner 

 bowl, and the original undivided gastro-vascular space to the space 

 between the two. If now the walls of the space be cemented together in 

 four horizontal curved lines just in the plane where the bottoms are 

 bending round to become the sides of the bowls, leaving four interspaces 

 between the ends of the lines, we should have the original space divided 

 into a central horizontal somewhat lens-shaped region between the 

 bottoms of the two bowls that would correspond to the central stomach, 

 and a peripheral vertical portion between the sides of the bowls that 

 would correspond to the peripheral gastro-vascular system ; central and 

 peripheral portions would communicate by the four interspaces between 

 the lines of fusion, which would correspond to the four gastric ostia. If, 

 further, the vertical peripheral portion be subdivided by four more lines 

 of fusion running vertically at equal distances apart, each connecting 

 above with the middle point of the corresponding horizontal line of 

 fusion, we should have the simple peripheral portion divided into four 

 parts, corresponding to the stomach pockets, by four vertical lines of 

 fusion, corresponding to the four interradial vascular lamellae, the ivl of 

 the figures. 



