1907.] 



NATURAL SCIENCES OF I'lll LADliLI'III A. 



405 



extrcnu> \v{{ odiiv of tlio mantle. Sending- a l)raiich anteriorly it bends 

 sharjily posteriorly and follows the mantle horder arunnd the visceral 

 mass and up the ri^ht side. The sections show (figs. C, D, Pal. a) this 

 vessel on lioth sides of the body. The artery becomes difficult to trace 

 at the forward left side of the mantle which borders the columellar 

 muscle. This is the vessel which Milne lulwards and AVegmann d(>scribe 

 as a vein, but tliis is certainly an error, as it does not connect with the 

 visceral cavity, but with that of the head. 



The foot of Ildliotis varies somewhat from that of the Old World 

 species so far as the circulation is concerneil. The single lateral pedal 

 artery of each side of the epipoilium in //. rufcscens (figs. C, D, Lpo) 

 is curiously enough represented in //. tuhcrculata, according to Weg- 

 mann, by two arteries, termed 1)y him the su]ierior pedal and inferior 

 external pedal arteries. The foot is pierced freely by blood sinuses, 



Fig. D. — Transverse section through middle of cohunellar muscle ot" //. rvfes- 

 cenn. Ao, anterior aorta; Cn, cohunellar muscle; G, (P, fnonad; K, anterior 

 portion of rifilit kidney. I'or other lette^rs see explanation of plate. 



and injections pass with ease throughout its entire extent even from 

 arteries into veins or vice versa. It is therefore readily seen that the 

 blood of the foot is collected into a large median sinus, of which two 

 sections may be seen in fig. D, PS. At the front end of the foot this 

 makes a gentle bend upward immediately behind the pleuro-pedal 

 ganglia, and turning to the left along that side of the columellar muscle 

 proceeds posteriorly. Throughout the remainder of its coiu'se, this 

 sinus is partially imbedded in the anterior lobe of the right kidney 

 (fig. D, PS), which it drains while en route to the basi-branchial sinus. 

 Its lumen is of more than average size and may be readily followed. It 

 is therefore with questioning that one considers Wegmann's statement 

 to the effect that anteriorly this sinus in //. tubercidata empties into the 

 visceral cavity. Can there be such a radical difference between two 

 27 



