LEPTOMEDUSAE. 147 



Gastrovascalar system. — The central .stomach is small, only about 15 mm. 

 in diameter ; the mouth widely open, without any sign of proboscis, and 

 surrounded by a simple circular thickening. Twenty-eight radial canals 

 arise from the stomach ; five of these then branch dichotomously so that 

 thirty-three extend to the margin. The canals, both radial and circular, are 

 very broad (PI. 33, fig. 4). 



Gonads. — The gonads are proximal (PI. 33, fig. 4); small, circular, and 

 flat. Several of the canals appear to lack them, but it is doubtful whether 

 this is a normal condition. Sexual products are not mature : the speci- 

 men is apparently a male. 



The specimen is entirely colorless, the entodermic system being merely 

 more opaque than the hyaline disc. 



Halitrephcs maasi must be regarded as an intermediate form. It is 

 one of the few members of this class which has been taken in a closing 

 net at a known depth. The occurrence of this colorless form at three 

 hundred fathoms shows the danger of speculating on pigmentation as an 

 indication of bathymetric range. 



Leptomedusae. 



The genera of Leptomedusae without otocysts have recently been re- 

 arranged by Maas (:04 b )and Browne (:07), who, though differing as to 

 whether condition of canals or of marginal organs is the more important, 

 agree that the two families, Cannotidae and Thauinantidae, between which 

 Haeckel ('79) divided these genera, are purely artificial groupings. In- 

 deed, one subfamily of the Cannotidae, the Williinae, has been shown by 

 Browne (: '96) to belong to the Anthomedusae, since the gonads lie on the 

 walls of the manubrium, not on the radial canals. According to Maas (: 04 b ) 

 the remaining Cannotidae are to be divided into two families, Berenicidae 

 and Polyorchidae, according as they have branched or pinnate canals ; but 

 Browne (:07) has recently maintained, and I believe correctly, that a 

 more important character than the condition of the canals is the presence 

 or absence of the peculiar marginal clubs known as cordyli, (heir presence 

 characterizing the family Laodiceidae, which includes most of the genera 

 grouped by Maas under the heading Berenicidae, as well as several from 

 the Thaumantidae as defined by Haeckel ('79). The systematist must 

 recognize the weakness of a classification based upon a single character, 



