REPORT ON THE DEEP-SEA MEDUSA. ci 



between the four primary perradial (Melicertidse, Octocannidaa, Aglauridae, Pcctyllidaj, 

 Pis. III. -VIII. ; System, taf. viii. fig. 10; taf. xvi, xvii.). In the iEquoridae, where 

 the number of the radial canals multiplies indefinitely (20-80 and over), the number 

 of the genitalia fastened to them increases correspondingly (System, taf. xiv., xv.). 

 In the simplest case, each reproductive gland forms a simple, ridge-shaped thickening in 

 the suburethral wall of each radial canal. In many Craspedotae, however, this ridge is 

 divided into two lateral halves, between which the median line of each wall remains free 

 from the sexual products. The two paired halves of these reproductive ridges lie further 

 asunder in proportion to the developement of a longitudinal radial muscle in this median 

 line (PI. VIII. fig. 9). They sometimes hang down in the umbrella cavity as two 

 parallel folds (e.g., iEquoridaa), sometimes extend like leaves in the surface of the 

 subumbral wall (Geryonidae). The canal usually forms a caecal evagination into the 

 genital ridge on the subumbral wall of the radial canal, whether it remains simple, or is 

 divided into two paired halves, so that it assumes the form of a pendant vesicle, sac, or 

 tube (Pis. III.-VIIL). Further complications in its formation also arise when the 

 genital band is arranged in folds ; the depressions between the separate folds may also 

 become so deep that it is divided into numerous separate vesicles (e.g., Olindias, System, 

 taf. xv. fig. 11). The Octorchidse, a sub-family of the Eucopidaa, are distinguished by 

 each of the four genitalia, being divided into two pieces lying far apart ; the proximal 

 part lies on the ascending radial canal of the umbrella peduncle (fig. N, s 2 ), the distal 

 part on the descending radial canal of the subumbrella (fig. N s', p. 190); here eight 

 genitalia also come on four radial canals. 



§ 142. Genitalia of the Acraspedse. The reproductive glands in all Acraspedse (in 



constant and typical contrast to the Craspedotae) are developed from the endoderm of 



the gastrovascular system. The sexual products in process of development first 



appear from the subepithelial germinal layer, in the depth of the gelatinous mesoderm, 



and are there enclosed in special fulcral capsules (PI. XXV. fig. 7, zz). When mature, 



they break through these chorion sheaths, and fall freely into the gastral space from 



which they are emptied out through the oral opening. In the Acraspedse, as in the 



Craspedotse, the formation of the reproductive cells takes place sometimes more in the 



central part of the gastrovascular system, sometimes more in the peripheric part. Whilst 



in the Craspedotse, the central gastral genitalia appear to be the primary formation, and 



the peripheric vascular genitalia to be derived secondarily from them, in the Acraspedse, 



the development of formation is probably reversed. It is precisely the older and 



more simply constructed Tesseroniae (the Stauromedusse, Peromedusae, and Cubomedusae), 



that have bursal genitalia, which are developed in the subumbral wall of the four wide 



radial pouches, or of the wide peripheric coronal connecting them ; in the younger and 



more highly developed Ephyroniae (the Discomedusse), the genitalia pass more and more 



centripetally from the subumbral wall of the radial pouches or peripheric coronal sinus, 



