626 ARTHUR WILLEY. 



ill the post-braucUial genital region. The mouth of each pit 

 is about 1 mm. in diameter. 



At a glance the pits appear to be regularly paired^ but a re- 

 examination has shown that they are not quite so regular as 

 represented in fig. 1. 



In the fresh condition the sides of the genital region of the 

 body were occupied by elongated, somewhat pyriform bodies, 

 which caused definite ridges on the external surface. These 

 projections were caused by the gonads. The individual was a 

 mature male. 



The dermal pits lie in the submedian line, in direct con- 

 tinuation from the branciiial groove, and the most anterior 

 pits invade the posterior extremity of the branchial region, in 

 consequence of which a number of the outer pores of the 

 posterior gill-slits do not open near the surface of the body, 

 but deep down at the base of the dermal pits. 



The last newly formed gill-slit on each side opens directly 

 from the gut into the base of a dermal pit; and at first I 

 thought they represented the intestinal pores (Darmpforten) 

 described by Spengel (discovered originally by Schimkewitsch). 



Under some circumstances it might be very difficult to 

 distinguish true gill-slits from intestinal pores. 



Spengelia differs from Schizocardium and Glandiceps in 

 the absence of anterior intestinal pores. I am unable to say 

 anything about the posterior intestinal pores, as ray specimen 

 was incomplete. 



Transverse sections show that the dermal pits of Spengelia 

 are remarkably deep, extending through more than half the 

 thickness of the body, and actually branching amongst the 

 gonads. They appear to serve for the irrigation of the gonads. 

 If anyone saw a single section passing through the middle of 

 a dermal pit, he would say that Spengelia possessed genital 

 pleurae. Perhaps these pits owe their origin to an incomplete 

 fusion of genital pleurae with the body-wall; or they may 

 merely represent local depressions of the floor of a branchio- 

 genital groove. 



Apart from their connection with the gut by means of the 



