DEVELOPMENT OF BALANOGLOSSUS KOWALEVSKII. 4513 
followed into the layer of nerve-fibre, which is always more or 
less developed at the base of the ectoderm cells over the whole 
body. These cells compose the larger part of the skin of the 
proboscis and collar. Amongst them are distributed cells 
which probably secrete mucus, &c. These cells are of several 
kinds. First,in the skin of the proboscis are large goblet cells 
whose nucleus alone stains (fig. 75, mu’). Next, in the skin of 
the back of the collar and of nearly all the rest of the body 
excepting those parts in which concentrations of nervous 
tissue are found, almost the whole tissue is made up of large 
cells full of some substance probably lubricating also, which 
does not stain. These cells are sufficiently represented in figs. 
72 and 72a, which are, however, from B. minutus. In parts 
of the skin which are of this kind the long cells of the ecto- 
derm are comparatively few in number, and thus the skin has 
a spongy consistency which is very characteristic. This is 
true of the skin behind the collar in B. minutus, B. sal- 
moneus, and B. Robinii. There is a general similarity 
between the skins of all these forms, and probably their struc- 
ture is the same asin B. Robinii. This statement, however, 
only rests on the evidence of sections, as no teased preparations 
were made of B. minutus. In the skin of the collar and 
proboscis especially a small number of nuclei may be seen in 
the higher layers of the skin. Whether these belong to young 
cells of the tailed series or of the secreting type was not deter- 
mined. Another set of small, generally bifid secreting cells, 
are found in the proboscis skin; the contents of these cells are 
granular. 
There is one other point of importance in treating of the 
skins of these forms, viz. the constant presence in teased pre- 
parations of large spindle-shaped cells (fig. 77, ¢). As the 
result of many observations it appeared nearly certain «that 
these had really been broken off from the ends of the long 
ectoderm cells. Unless care was taken in the preparation this 
frequently happened, many of the ectoderm cells being broken 
and therefore without nuclei, and hence the probability that 
this was the origin of the spindle-shaped cells. Since these 
