15S I)()XI)KI{SIA ( ALIKOIJXICA. 



(lovol()])s branches, in roality ojicninss, coninuinicating with iiumcrous lacunae 

 in the dorsal crcsl-liivc portion of the liody. Those in turn connect with others 

 of less extent in the lateral regions and through these with the pedal sinus. In 

 the head region the aorta breaks up into several sinuses which make theii' way 

 through the anterior pedal gland to connect with the pedal sinus antl the more 

 lateral spaces just described. In the posterior end of the animal the blood 

 accuMiulates in large sjiaces surrounding the intestine and coelomoducts and 

 pours into th(> lieart l)y means of a sinus passing dorsally on each side in the 

 neighborhood of the reno-pericartlial openings. The pedal sinus contimies 

 backward to the cloaca then ixxsses dorsally into a space beneath the shell gland 

 and from tliere into vessels leading to the heart. 



Tlie gotuxd is distinctly paired, the two divisions being in contact only in 

 I lie middle of the liody. Elsewhere they are widely separated by means of the 

 dorsal aoita. In th.e mid section spermatogonia are fairly numerous and at all 

 points ova are conunencing to develop. In the heart region the glands narrow 

 and (•(imnnuiieate with the pericardium, which ]iosteriorly conununicates also 

 with the co(>lonio(lucts opening into the cloaca. The dorsal division of these 

 tubes is comparatively slender and is composeil of cubical ciliated cells without 

 signs of glandular activity. No trace of a seminal receptacle is visible unless 

 what appears to lie the anterior end of the ventral section may be so considered. 

 This lower division, or shell gland, is composed of rather low colunmar cells, 

 tending to form longitudinal ridges, but they likewise are inactive. 



Beneath the single opening of the coelomoducts the cloacal wall is developed 

 into an outjiouching which in the adult animal may develop copulatory spicula 

 or some gland connected with the egg-laying jirocess, though in the present 

 specimen such functions are purely hypothetical. In shape this outgrowth 

 resembles a thick set Y, having a median undivided section which opens into 

 the cloaca and on the other hand connects with a blind ])oiu'li on each side of 

 the mid line. The walls are not unlike those of the shell gland, consisting of 

 columnar cells which are richly ciliated. 



Th(- cloaca or mantle cavity in this sjieeimen is of unusually small size 

 though it may increase in diameter as the mature condition is approached. A 

 glance at Plate 6, fig. 2, will show that in this species the dorsal commissure 

 uniting the lateral nerve cords is placed unconunonly near the cloacal opening. 

 If in the adult the commissure is customarily placed it might readily be 

 shifted by the active growth and enlargement of the cloaca. 



The nervous system is typical. The brain is situated posterior to the atrial 



