280 
J. STEPHENSON. 
This tissue is in two lateral masses, there being none covering 
the dorsal vessel (here still double), which lies directly on the 
gut. The tissue does not, as a whole, come in contact with 
the inner surface of the parietes — i. e. it does not fill up all 
available space between gut and body-wall, though connec- 
tions with the body-wall exist in the form of strands of 
reticular nucleated tissue. The masses I take to be the 
dorsal mass of the oesophagus in an early stage. 
At one place on the left side, at the periphery of this mass, 
is an aggregate of a few cells which are distinguishable from 
the rest (PI. 19, fig. 10). These cells, about a dozen in 
number in the section which shows them best, and extending 
only through a few sections, are mostly elongated in one 
direction and 12-20 fx in greatest length. The nuclei are in 
most of the cells somewhat obscured and difficult to see ; 
they are spherical or ovoid, 3*5-4 y. in greatest measurement, 
with a spherical homogeneous nucleolus of relatively con- 
siderable size, surrounded, in the cases where it is best seen, 
by a clear circular space ; nucleolus and clear space a, re 
rather excentrieally situated. The peripheral chromatin is 
distributed as distinct and fairly large granules. Some 
nuclei have two nucleoli; in other cells two relatively small 
nuclei are in close apposition ; but I could not discover any 
mitotic figures (compare the various appearances of the nuclei 
in PI. 19, fig. 10). The cytoplasm stains moderately deeply, 
but not so deeply as the chromophil substance of the 
adult cells; and not quite evenly, haviug a granular texture 
which is closer and more homogeneous in some parts than 
others. 
These cells do not help to form the slightly pinkish (eosin 
staining) reticulum into which the main portion of the dorso- 
lateral pharyngeal masses seem to be dissolving. The cells 
are in several cases connected together among themselves, 
perhaps because nuclear division goes on in advance of division 
of the cell -body (see the upper left-hand part of the figure). 
No peritoneal membrane surrounds the mass ; while on the 
body-wall the cells lining the ccelomic cavity are cubical with 
