REPORT ON THE SIPHONOPHORiE. 143 



The two nectophores of the second subfamily, Diphyopsid.se (PL XXXIII.), are also of 

 nearly equal size and similar form ; but they are pyramidal, pentagonal, and placed one 

 behind the other. Their junction is very loose in Galeolaria, whilst in Diphyes and 

 Diphyopsis the apical part of the second is hidden in the hydrceciurn of the 

 first nectophore. The sharp edges are often elegantly denticulate, and the hyaline 

 jelly-substance of the umbrella is rather hard and firm, cartilaginous, as also is that 

 of Abylidse (Pis. XXXV. -XL.). 



The differentiation of the two nectophores attains the highest degree in the third sub- 

 family, Abylidse. The first (proximal or apical nectophore, often also called superior or 

 anterior) is here always symmetrical and much smaller than the second (distal or basal 

 nectophore, often called inferior or posterior) ; this is more or less asymmetrical. Both 

 nectophores are here polyhedral, prismatic, or truncate-pyramidal, with numerous poly- 

 gonal faces and sharp prominent edges. The form of the second nectophore and its basal 

 ostium is especially characteristic ; it offers three prominent wings in Abyla (trigona), 

 four in Bassia (tetragona), and five in Calpe (pentagona). 



Canals of the Nectophores. — Each of the two nectophores constantly possesses four 

 radial canals in the subumbrella, which are united above the velum by a circular canal. 

 The size, course, and form of the four vessels are very variable, according to the place of 

 their apical junction, where the nectocalycine duct, coming from the top of the stem, 

 enters into the subumbrella. This point of junction is usually placed not at the apex of 

 the nectosac but in its ventral median line, more or less dislocated downwards, so that 

 the ventral canal (cv) is shorter, and the dorsal (cd) longer than the two symmetrical 

 lateral canals (ex right, cl left) ; the latter are often more or less curved or loop-shaped. 

 The ventral canal is very short, rudimentary, or even lost, in the first nectocalyx of 

 Galeolaria, because here the point of junction has quite descended, and the nectocalycine 

 duct enters into the base of the subumbrella, instead of into the apex. The opposite 

 dorsal canal is so much the longer. 



Hydrceciurn. — The differences which the hydrceciurn offers in the Diphyidse, have 

 been already mentioned above (p. 93). The Prayidse are distinguished by a cylindrical 

 hydrcecial canal open at both ends, composed of the ventral grooves of the two opposite 

 nectophores, fitting one into another. Galeolaria has no true hydrceciurn, since the 

 apex of the second nectophore is simply attached to the base of the first, and the 

 siphosome is suspended freely between them. All other Diphyidse have a conical or 

 campanulate hydrcecial cavity on the ventral side of the first nectophore, and as its 

 continuation, a hydrcecial canal on that of the second ; this is sometimes an open groove, 

 protected by two overlapping wings, at other times a closed canal, produced by 

 concrescence of the two wings. 



Somatocyst (cs). — The acrocyst or somatocyst (" Saftbehalter ") is wanting in the 

 Prayidse and in Galeolaria ; it may be replaced in the former by the ascending pallial 



