DORYMENIA PERONEOPSIS. 227 



The vessels to the gonad, and the communication of the dorsal vessel 

 or aorta with the channels in the head region are of the usual type. These 

 last named sinuses are relatively small yet can readily be followed past the 

 anterior pedal gland and about the buccal wall to a small ventral median sinus 

 originating immediately posterior to the outlet of the anterior pedal gland. 

 Above the forward end of the foot this median sinus is of more than usual width, 

 but throughout its entire extent to the posterior end of the body it communicates 

 here and there with the overlying visceral sinus. As the hinder end of the 

 animal is approached these two blood spaces unite at more frequent intervals 

 and finally fuse completely. The single channel thus formed communicates 

 with the posterior end of the heart. 



No distinct branchial apparatus exists in this species. The walls of the 

 cloacal chamber are smooth and ciliated, and as they are in intimate contact 

 with the visceral sinus they may function in the respiratory process. 



The present specimen, although of considerable size, is sexually immature, 

 and it is altogether possible that during the breeding season the general appear- 

 ance of the accessory reproductive apparatus may be considerably altered, 

 though the configuration of the component organs will probably remain about 

 as that shown in the reconstruction (Plate 7, fig. 7). The gonad exists in the 

 form of two slender tubes ending bUndly anteriorly and separated widely by 

 the dorsal aorta. Posteriorly they enter the pericardium, whose size and 

 general appearance in sections are similar to what has been found to exist in 

 Strophomenia. The gonoducts, in the form of slender tubes, arise from the 

 posterior border of the pericardial cavity and extending downward and forward 

 join the shell gland or ventral section. 



The dorsal section of each coelomoduct is a tube of approximately even 

 cahbre throughout (Plate 8, fig. 6), and is composed of cubical cells, possibly 

 ciUated and certainly without any signs of glandular activity. The ventral 

 section is of somewhat larger size, and is Ukewise formed of cubical cells in which 

 there are very small quantities of a darkly staining secretion. At the junction 

 of the dorsal and ventral sections a small sacculation may represent the char- 

 acteristic seminal receptacle though it contains no spermatozoa. 



Ventral to the coelomoducts are two diverticula each of which communi- 

 cates with the cloacal cavity and probably contains a spicule though the process 

 of decalcification has wiped away all traces. Retractor muscles attach to the 

 outer surface of the blind end and on the other hand extend anteriorly to become 

 inserted in the body wall. Protractors Ukewise attach themselves to the sheath, 



