718 A. T. MASTERMAN. 



the anterior wall of the pharyus. Its total length is usually 

 about "14 nim.^ and its breadth about "02 mm. It usually 

 has for about four fifths of its length a central lumen, which 

 opens posteriorly into the pharynx, and terminates anteriorly 

 in a vai'iet}^ of ways. Fig. 1 shows the subneural gland cut 

 throughout nearly its whole length. The lumen usually, as in 

 tliis case, contains a rod of glandular secretion of the nature 

 of mucus. At its apex the gland is bent dorsally. Throughout 

 the gi-eater Y>Cbvt of its extent its wall is composed of a simple 

 glandular epithelium, but at its distal extremity the cells 

 show a chordoid modification. The cells become vacuolated 

 and reticular, producing the well-known chordoid structure of 

 the ^^notochord" of Balanoglossus, Actinotrocha, and the 

 Yertebiata. This is well seen in figs. 8 and 9. The extent 

 of this chordoid modification varies immensely, and it is only 

 the largest (oldest) individuals which show such a complete 

 chordoid apex as in figs. 8 and 9. This specimen also shows 

 a not uncommon feature in the complication of the central 

 lumen. In the apex it forks out into two lateral canals as 

 well as the median central canal (fig. 7) — a character also 

 found in some Enteropneusta. 



The relationships of the subneural gland to the pharynx 

 have been already described elsewhere (10), and its connection 

 with dorsal pharyngeal and peripharyngeal grooves has been 

 demonstrated. In fig. 3 the commencement of the dorsal 

 and peripharyngeal grooves is shown with their numerous 

 unicellular glands. The commencement of the pleurochord 

 is seen in fig. 5. It is important to notice the relationshijis 

 of the subneural gland to the pre-oral and collar cavities. 

 It is bounded laterally throughout its extent, except at the 

 apex, by the walls of the two collar cavities, and ventrally by 

 the wall of the pre-oral cavity. Above it the two collar 

 walls form a median dorsal mesentery (fig. 2), and then 

 diverge under the ectoderm to form the dorsal blood-sinus. 

 At its distal end or apex the subneural gland reaches just 

 beyond the collar walls, and plugs up the mouth of the heart, 

 as described below (figs. 1 and 2). 



