550 MAYNARD M. METCALF, 



right side coonects with the neural gland. The latter is large and lies 

 on the right side of the ganglion, one wall being closely appressed to 

 the surface of the ganglion (Fig. 88). This wall, next to the brain, 

 is composed of a single layer of cubical cells. The opposite wall, 

 distant from the brain, shows a similar cubical epithelium whose cells 

 are in active proliferation. The lumen of the gland contains loose 

 masses of cells derived from this source. These are seen to be large 

 and vesicular, like the cells in the lumen of the gland in Ecteinascidia 

 and Terophora. Many of them are degenerating. A lobulated mass 

 of glandular cells pushes back from the gland (Fig. 86), and from 

 its connection with a large gangliated nerve (the rapheal nerve) and 

 two muscles (apparently the rapheal muscles) it is easy to identify it 

 as the rapheal duct. This is seen also from the fact that it follows the 

 course of the dorsal lamina. It is of considerable size and contains 

 vesicular cells like those of the main gland. It runs but a short 

 distance into the raphe. 



A large richly gangliated nerve runs back from the brain (Figs. 82, 

 86 and 87 r.n). That it is the rapheal nerve is shown by the great 

 number of its ganglion cells, by its median position, and by its 

 association with the rapheal duct and the two rapheal muscles 

 (Fig. 84 r.m). It passes back along the median line underneath the 

 peculiar muscles on the dorsal side of the visceral mass (cf. Fig. 87). 

 Its posterior end pushes in between the stomach and the ovary and 

 soon disappears. It is richly gangliated throughout its whole length. 



In my specimens, as in Moselet's figures which I have copied 

 in Plate 40, Figs. 82 and 87, the pair of large nerves arising from 

 the lateral angles of the triangular brain run forward toward the 

 sides of the oesophageal aperture (Fig. 86). The median angle of the 

 ganglion is posterior and gives rise to the great rapheal nerve ^). The 

 gland lies chiefly behind the brain, corresponding in position to the 

 so-called "sense-organ" of Moseley. This corresponds to Moseley's 

 fig. 3 (Fig. 87), showing the whole visceral mass, and also to his 

 fig. 4 (Fig. 82) showing the ganglion and "sense organ" under higher 

 magnification. Hekdman's fig. 11 (Fig. 83), I am unable to under- 

 stand. He shows the dorsal tubercle lying far behind the ganglion, 

 and show it as if lying dorsal to the gland; unless, indeed, he in- 

 tends the figure for a ventral view of the organs, in which case he 

 figures the transverse muscles as lying below the brain and gland, 



1) The absence of posterior siphonal nerves is probably due to 

 the absence of the atrial siphon and its muscles. 



