602 CHRISTIAN CHAMPY AND H. M. CARLETON 
sections of such nuclei confirm the existence of these incisions, 
which we have observed in non-striated muscle from the 
intestine in Amphibia (see Pl. 24, fig. 2), in Mammals (muscle 
layers of intestine of cat), and in certain invertebrate muscle- 
fibres, e.g. heart of Helix as shown in Pl. 24, fig. 6. 
Finally, we have noted similar folds in the nuclear mem- 
brane of developing oocytes (already described in Section 3), while 
a peri-nuclear reticulum—possibly comparable to that found in 
smooth muscle-cells—has been described by Retzius in the 
spermatozoa of certain Gasteropods as shown in Text-fig. 3, B. 
8. THE UNFOLDING OF INVAGINATIONS IN THE NUCLEAR 
MEMBRANE. 
It seems certain that nuclear. folds and incisions expand 
under certain conditions, thus altering both volume and shape 
of the nucleus. That such a phenomenon occurs during 
differentiation of some cells is shown by the following example : 
In Urodele Amphibia there exists a layer of lymphoid tissue 
surrounding the liver. Study of the lymphocytes in this layer 
(see Pl. 23, fig. 5) show that their nuclei, though round or oval, 
bear a large number of narrow incisions. The latter can be 
observed in various degrees of ‘ deployment’ in these cells, 
and there is no doubt that polymorphonuclear leucocytes can 
be formed in this manner from lymphocytes in some Amphibia 
—a point in favour of the ‘ Unicist ’ theory of blood-formation. 
The persistence of some of the nuclear folds gives rise to the 
lobulation characteristic of the polymorphonuclear leucocyte. 
Mutual cell-pressure may apparently in certain cases 
inhibit expansion of the nuclear membrane. We have observed 
an instance attributable to this in cells from the epidermal 
and sub-epidermal tissues of the sucker of the fish Lepado- 
gaster guannii. ‘This is illustrated in Text-fig. 5, a and B. 
9. INTRANUCLEAR RODLETS, ETC. 
Intranuclear rodlets and allied structures, which are only 
found in highly specialized cells such as spermatids or certain 
red blood corpuscles, are responsible for the shape of the 
