350 Mary R. Cravens and Harold Heath, 



more rarely in tlie later stages of mitosis. Spermatids occur much 

 less frequently but are readily recognized by their small sized, dense 

 and darkly staining nuclei. Fully developed spermatozoa are very 

 abundant and, arranged in packets, occupy most of the central 

 portions of the sac. The head of the sperm is elongated, needle- 

 like and considerably curved. In the majority of cases the reagents 

 have destroyed the tails, but in a few rare instances they exist and 

 are at least fully twice the length of the head. 



Each testis is surrounded by a muscular coat (Fig, 8, 17), 

 which in surface views is seen to consist entirely of circular bands. 

 These are especiallj^ abundant about the duct and the adjoining 

 section, but more distally the fibres become less numerous and may 

 finally disappear almost entirely. In some cases tliose attached to 

 the gland may not be superficially placed throughout their extent, 

 but on one side may pass inwardly leaving a small outlying crypt 

 (Fig. 17), filled with sex cells, which communicates with the main 

 body of the gland by a small pore. The presence of such a powerful 

 musculature indicates that the sex products are probably very forcibly 

 discharged but under what circumstances it is impossible to state. 



As in typical hoplonemerteans, the central nervous system lies 

 imbedded in the body parenchyma entirely internal to the muscles 

 of the head and trunk, and in cleared preparations and to some 

 extent in fresh material its main features may be determined. The 

 four-lobed character of the brain cannot be made out in surface 

 views, but sections show the division into nearly equal dorsal and 

 ventral ganglia. These are united by two commissures, encircling 

 the proboscis sheath, of which the ventral band is considerably 

 larger and more anteriorly situated than the dorsal one. From the 

 posterior ends of the brain the large lateral nerve trunks pass 

 downward and backward usually external to the main intestinal 

 lobes [though frequently overlapped by some of the smaller diverticula 

 (Fig. 2)], and in this position proceed to the posterior end of the 

 body where they again change their course, coming up between the 

 gut pouches to unite on the dorsal side of the rectum a short 

 distance back of the union of the median and lateral blood vessels 

 (Fig. 9). 



Regarding the histological character of the brain and lateral 

 cords the constituent elements and their relations are somewhat 

 the same as in the species described by Büeger (1895), Montgomery 

 (1897) and Thompson (1902). The small cells of Büeger (No, I of 



