30 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



consent are ectodermal. And while we are being led by facts such as 

 those just mentioned above to wonder just a little whether after all the 

 position of the Cubomedusa? among the Acraspeda is so firmly assured 

 doubting some, yet in the frame of mind of one who " fears a doubt as 

 wrong " -the velarium suggests itself as another point in question. 

 Haeckel does not hesitate to state emphatically that the velarium of the 

 Cubomedusae and the velum of the Craspedote medusa are only anal- 

 ogous, but the reasons that he gives (sie sind unabhangig von einander 

 entstanden, und ihre Structur ist zwar ahnlich, aber keineswegs iden- 

 tisch ; namentlich das Verhalten zuna Nervenring ist wesentlich ver- 

 schieden : System, p. 42(5) somehow do not produce so much impression 

 upon one as the very velum-like appearance of the velarium itself. The 

 origin from the fusion of marginal lobes is not as yet a matter of obser- 

 vation, and the relation to the nerve ring is not essentially different from 

 that of the velum to the lower (i. e. inner) nerve ring in the Craspedotas. 

 The four frenula and the diverticula from the gastro-vascular system 

 seem to be the chief differences in structure after all, and these Haeckel 

 evidently did not think worth mentioning. This speculation, as to the 

 possible relation of the CubomedusaB to such forms of the veiled medusas 

 as Liriope, though it may be very tempting, is scarcely fruitful enough 

 to repay much effort on the part of either reader or writer. The whole 

 subject must remain uncertain until the facts of the development of the 

 Cubomedusa? are known. 



If the structure of the vascular lamellae of the internal system has 

 been made clear, the appearances of the vertical and horizontal compo- 

 nents in the figures will be understood without much further explana- 

 tion. The four vertical strips in the interradii (ivl) have been already 

 referred to in the figures of the cross-sections of both Charybdea and 

 Tripedalia. In the longitudinal sections of the two jelly-fish through the 

 interradii, the vertical lamellae are cut throughout their entire length 

 from stomach to connecting canals (Figs. 5-20, ivl). The horizontal 

 cross-pieces at the tops of the vertical lamellse also appear in several of 

 the figures. Fig. 36 represents the appearance that would be given by a 

 longitudinal section taken through any portion of the upper part of the 

 bell except in the interradii, or in the perradii, through the gastric ostia. 

 The horizontal vascular lamella (hvl) is shown connecting the endoderm 

 of the stomach (ens) with that of the stomach pocket (enp). In a longi- 

 tudinal section directly through an interradius (Fig. 5 or 20) the hori- 

 zontal lamella is cut just at the point where it joins the vertical, so that 



