MUSEUM OF COMPARATIVE ZOOLOGY. 25 
I was too early or too late for embryological material, although from 
some indirect evidence drawn from what follows I am inclined to think 
I was too early. 
The youngest stocks found I obtained in large numbers, and they 
were of almost exactly the same age. Moreover, they agreed with the 
youngest stages found by Leidy and figured by him (’84, Plate I. Figs. 
5, 6, 7). I have represented some of these in Plate V. Figures 31, 32, 
and, enlarged, in Plate II. Figure 15, and Plate V. Figure 46. 
I have already (pages 3-6) called attention to some of the characters of 
the stalks of these young individuals. It remains to mention the “ basal 
plate” of such stocks. : 
Unlike its condition in the adult, the “basal plate” is a relatively 
large organ of elongated cylindrical form (Plate II. Fig. 15). Its outer 
epithelium consists of sharply demarked cells, cuboidal above, columnar 
below. This epithelium has given rise to a cuticula thin and dense 
above, and thicker and less refractive below. The columnar cells are 
somewhat less deeply stained than those at the end of the “ basal plate” 
farthest from the two stalks. Their nuclei lie at their inner ends. 
The outer part of the cell contains spherical masses of granules. On the 
whole, it stains less deeply than the inner end. Finally, one always 
finds particles of dirt closely adherent to the under and lateral aspects 
of the basal plate. 
These facts I interpret as follows. The columnar cells of the under 
side are glandular, and secrete a sticky substance which causes the ad- 
herence of the surrounding particles of dirt, and thus serves to anchor the 
young stock.1_ The tissue of the interior of the “basal plate” is remark- 
able, and difficult of interpretation from sections alone. In such sections 
one sees bands running through the middle region and crossing at various 
angles. Each of these “ bands ”’ is a nucleated cell, and probably repre- 
sents a muscle fibre (cf. Plate V. Fig. 46). One sees also fibres having a 
different appearance running radially from the base of the stalk to the 
columnar cells of the “basal disc” over quite a long stretch (Plate IT. 
Fig. 15). In addition to these protoplasmic structures there are long 
clear spaces which are bounded by thin membranes and contain occa- 
1 Seeliger (’90, p. 573) finds in Pedicellina a glandular differentiated zone on the 
base of the stolon, where it comes in contact with foreign bodies. This, he says, 
can be traced unbroken through the entire length, especially in young stocks, con- 
sisting of few individuals. The foot gland of Loxosoma is an organ fulfilling a 
function similar to that of the glandular cells of the stolon, but an homology of the 
two organs can hardly be maintained. 
