312 
As in Raja and as in other cases, the apparatus of Scyllium 
is a transient one, and, after slowly degenerating from the critical 
period of 32 mm, it disappears finally, soon after the embryo hatches 
out with a length of about 10 cm. 
Acanthias vulgaris and Mustelus vulgaris present cases, 
where a very reduced and rudimentary transient apparatus is deve- 
loped. 
At an outside and extreme estimate, while in Scyllium and 
Raja there must be in every instance more, rather than less, than 
600 ganglion-cells, in Acanthias not more than 50, and in Mustelus 
vulgaris not more than 12 ganglion-cells are developed. In Raja, 
and probably in Scyllium also, it is an under-estimate to give 600 
as the number, whereas in Acanthias and Mustelus vulgaris 
it is a slight exaggeration to say there are as many as 50 and 12 
respectively present. But in the latter two cases some few may have 
been overlooked, for the embryos left something to be wished-for in 
the matter of their state of preservation. 
The above numbers will, then, be used as approximations only. 
Degenerate as is the apparatus in Acanthias and Mustelus, 
it presents characters similar to those ascribed to that of Raja, as 
the drawings and notes before me prove: and one can distinguish 
central cells, peripheral cells, ganglion-cells in the myotomes, and 
nerve-processes of cells in both of these fishes. 
There exists no room for doubt, that in both the insignificant 
apparatus developed degenerates and disappears, for, even in early 
stages, some of the cells show signs of atrophy. 
Torpedo, of which there is an extensive series of sections in 
my possession, never presents any trace of a transient apparatus, and 
this holds for every embryo examined, and the series reached up to 
the critical stage. 
In this form, therefore, my search has been as barren of results 
as the earlier one of PAuL Mayer. As a rule, for there may, for 
anything I know to the contrary, exist individual exceptions, no tran- 
sient ganglionic apparatus whatever is present in the development of 
Torpedo. Now, this would be explicable as a result of uterine de- 
velopment on the larva or phorozoon, i. e. as due to complete para- 
sitism of the latter, but, apparently unfortunately, two other forms with 
uterine development do present us with such an apparatus, albeit in 
reduced form. 
For several years the whole affair was an enigma to me, and 
