REPORT ON THE DEEP-SEA MEDUSAE. Ixxxix 



completely obliterated ; the radial canals may also be completely obliterated here 

 (Solmonetidse), whilst in other Solmaridae, the pernemal gastral pouches remain 

 (Solmissidae), sometimes the internemal gastral pouches (Solmundinae, System, taf. xix. 

 xx. p. 346). 



§ 126. Pouch corona of the Acraspedae (" corona bursarum "). In contrast to the canal 

 corona of the Craspedotae, an essentially different form must be regarded as the typical and 

 original arrangement for the section of the Acraspedae, i.e., the pouch corona composed of 

 four wide, perradial pouches, which begin at the circumference of the central stomach, and 

 run in the subumbrella towards the umbrella margin where they are united by a coronal 

 canal. This typical quadripartite pouch corona of the Scyphomedusae, has been developed 

 from the simple gastral space of their ancestors the Scyphopolyps by the four interradial 

 taeniola of the latter being laid together and fused at four points (of equal height), or in 

 four streaks, by their upper dorsal parts and lower ventral parts. In this way four 

 small interradial nodes or narrow ridges are originated (PI. XV. figs. 2, 3, hi ; PI. XVI. 

 figs. 2, 3, ks), which form incomplete septa between four wide perradial pouches {bp). 

 The small fused nodes or the four narrow fused ridges in the mature Acraspedae still 

 contain a double layer (or a layer become simple by fusion) of endoderm cells, which 

 indicates this origin as acathammal plate (§ 101, PI. XXV. fig. 8). The marginal coronal 

 canal which connects the four broad pouches at the umbrella margin below the four 

 narrow septa, appears to be the marginal part of the originally simple gastral space of the 

 Scyphopolyps, which has remained open (therefore a " primary coronal canal "). This 

 typical primitive form of the coronal intestine of the Acraspedse is subject to varied 

 modifications, of which some (Flosculidae) are so bike the canal corona of the Craspedotas 

 that they may be confounded with it (" convergent selection "). 



§ 127. Eadial pouches (" bursas radiales," bs). The constant number of four of the 

 perradial pouches of the Acraspedas is very remarkable when contrasted with the frequent 

 variations of the number of four shown by the Craspedotae. The four perradial pouches 

 are orignally (phylogenetically) present, though they are often lost at an early stage. 

 They correspond to the four flat gastral pouches of the Scyphostoma, which are constantly 

 separated by four interradial taeniola. Frequent individual exceptions (especially 

 individuals with six or eight radial pouches) are of no importance, as they do not 

 transmit their peculiarity. The two sub-sections of the Acraspedaa, the Tesseronise and 

 Ephyronise, are, however, in general strikingly distinguished, as in the Tesseronise (Pis. 

 XV., XXVI. ), the four primary radial pouches always remain very large, and with the 

 coronal sinus belonging to them form the permanent principal component part of the 

 coronal intestine, whilst in the Ephyroniae (Pis. XXVII. -XXXII.) they have usually 

 undergone retrograde formation or become merged by fusion into the central stomach ; 

 they appear, however, to be of no great importance, and to have retreated towards the 

 peripheric pouch corona. The latter, which consists of at least eight, but usually of 



(ZOOL. CHALL. EXP. — PAET XII. — 1881.) M m 



