274 



ENTEROPNEUSTA FROM THE SOUTH PACIFIC, 



TRUNK. 



Branchial Region. 



The present species is characterised by the presence of a paired series of medial 

 gonads, mediad of the branchial grooves, in addition to the main lateral series (PI. XXXI. 

 Fig. 45). 



This is a feature which it possesses in common with the genus Glandiceps ; 

 while the fact that the branchial bars are united together by synapticula or cross- 

 bars (of which there are about ten in a vertical row) removes it from Glandiceps and 

 approximates it to Schizocardiuvi and the Ptychoderidae. 



It is a fact of topographical interest which is exhibited in horizontal sections 

 through the pharynx — such sections cutting the gill-bars transversely — that whereas in 

 the entire genus Ptychodera, the tongue-bars project into the cavity of the pharynx 

 beyond the septal bars, in Spengelia these relations are reversed, the septal bars 

 projecting into the pharynx beyond the tongue-bars. In other Enteropneusta the 

 conditions appear, judging from Spengel's figures, to differ according to the species. 



The lateral gonads appear in section at the level of the first gill-pore, but the 

 first genital duct occurs at the level of the fourth gill-pore ; the medial gonads com- 

 mence at the level of the fourth gill-pore. The genital ducts of the lateral series open 

 at the outer sides of the branchial grooves, while those of the medial series open at the 

 inner sides of the grooves. Apart from the medial genital ducts there are no accessory 

 ducts in the branchial region. Mediad of the lateral ducts may be found a lateral 

 (genital) blood-vessel. 



The gut in the branchial region is provided with a well-developed lower oeso- 

 phageal portion in the form of a deep groove, and the parabranchial ridges are nearly 

 as definitely demarcated as in the Ptychoderidae. 



The circular musculature of the body-wall is internal to the longitudinal muscu- 

 lature, instead of being external as it is in the Ptychoderidae; it agrees in its 

 disposition with that described by Spengel in Glandiceps, namely, the fibres arise at 

 the peripheral margins of the dorsal and ventral septa, and pass between the dorsal 

 and ventral sides of the body applied to the inner surface of the longitudinal muscu- 

 lature, the muscularis of the gut being independent of the dermal musculature. In 

 Schizocardiuvi, Spengel has shown that the muscularis of the gut, at least in the 

 branchial region, is derived from the dermal musculature. 



Genital Region. 



This region is characterised on the dorsal side by a right and left series of very 

 remarkable dermal pits which dip deep down between the gonads and actually pene- 

 trate to some degree amongst them. They probably serve for the irrigation of the 

 gonads, as suggested in my preliminary account of this species, and in this capacity are 

 to be compared physiologically with the subgenital pits of Discomedusae, and the 

 funnel-like depressions of Lucernariidae. 



