REPORT ON THE DEEP-SEA MEDUSAE. lxxxvii 



50-60, sometimes to from 100-200 and more, and is at the same time very inconstant 

 (System, taf. xiv., xv.). Their number is likewise variable and inconstant in the 

 Narcomedusse, where it never rises beyond 32 and usually amounts to between 

 11 and 20 (System, taf. xix., xx.). Whilst the radial canals of most Craspedotse, are 

 quite simple and unbranched, the three sub-families of the Cannotidse, are distinguished 

 by their being repeatedly ramified ; the radial canals of the Polyorchidse are beset with 

 csecal side branches, and consequently appear pinnated (Ptychogena, PI. II.) ; in the 

 Berencidae both the simple or ramified side branches of the radial canal, and their 

 direct process open into the coronal canal ; in the Williadse the radial canals are 

 bifurcated as in the Cladonemidse and Zygocannidae ; the bifurcations may also be 

 repeatedly dichotomised (System, taf. ix.). In those Craspedotse where a solid gela- 

 tinous gastral peduncle is developed in the centre of the subumbrella, each radial canal 

 is divided into two sections, an ascending peduncle canal, and a descending subumbral 

 canal ; the peduncle canal leads from the bottom of the stomach at the oral end of the 

 gastral peduncle to the base of the latter (in the bottom of the suburnbrella) ; the 

 subumbral canal from the last-named point to the coronal canal (fig. N). 



§ 124. Coronal canal of the Craspedotse (" canalis circularis," cc). In all Craspedotse 

 the radial canals are originally connected at the umbrella margin by a coronal canal 

 (" canalis circularis "). Its ontogenesis shows that it does not arise from the primary 

 gastral space remaining open at its peripheric margin, but by secondary anastomotic 

 formation of the radial canals. Whilst the latter are formed by the two endodermal 

 surfaces of the simple gastral space of the polyps becoming fused into four broad interradial 

 cathammal plates, the connective coronal canals at the distal end of the open radial canals 

 are formed by the separation of their two epithelial layers (dorsal and ventral endoderm) 

 at the distal margin of the endodermal cathammal plates. The marginal coronal canal 

 of the Craspedotse, is therefore formed in the same way as the secondary coronal canal of 

 the Cycloperise among the Discomedusae, whilst the primary coronal canal (or better, 

 " coronal sinus") of the other Acraspedae has quite a different formation (comp. § 126, 

 123). The tentacle canals, which pass into the hollow tentacles, run out in a distal 

 direction from the simple coronal canal of the Craspedotse. The " centripetal canals " 

 which run out from the coronal canal towards the middle of the subumbrella, where they 

 end csecally (§ 135), are sometimes developed in a proximal direction. 



§ 125. Festoon canal and radial pouches of the Narcomedusse. The order of the 

 Narcomedusse is distinguished by a peculiar condition of formation of the coronal intestine, 

 apparently completely different from that of the other Craspedotse. Broad caecal 

 pouches apparently proceed from the central stomachs, which are not connected by a 

 coronal canal, and resemble those of the Typhloperiae among the Discomedusse. More 

 minute comparative investigation however shows that they cannot properly be compared 

 with the latter, but that the typical fundamental form of the coronal intestine is the same 



