294 DR THOMAS H. BRYCE ON 
The Lepidosiren corpuscles thus resemble those of Salamandra in the possession of a 
very distinct equatorial band, but in their reticular structure they seem to correspond 
more to the description given of the corpuscles of the Frog. Taking all the possibilities — 
into account, I adopt the view that the reticulum is not an artifact, but that it 
represents a protoplasmic framework. This is possibly alveolar in arrangement, but 
i 
it is clear that the meshes of the reticulum exceed considerably the limit laid down by 
Burscuit for the true protoplasmic alveoli, and greatly exceed those of the optical 
reticulum seen in the protoplasm of the leucocytes. The erythrocyte is a much 
differentiated cell, and the structure described is evidently a secondary one. The 
whole protoplasm is fibrillar, but the framework is not necessarily fibrous or fixed. I 
believe rather that it is colloidal. I derive it from a vacuolated condition, in which 
the active protoplasm (Hyaloplasm) is greatly reduced, and it may well be that an 
original alveolar arrangement has been lost by the breaking through of mesh walls. 
The peripheral band must be either the cause or the consequence of the shape of the 
corpuscle. It disappears when the disc begins to round up for division, This suggests” 
the possibility that the appearance is due to a massing of the mesh walls. Further, in 
the angular interval between the upper and under layers of the membrane round the 
equator, there is a space (fig. 2, Pl. I.) occupied by the fibrillee of the ring cut across. 
When the corpuscle rounds up, this space disappears, and the band is replaced by a 
reticular formation. ' 
These considerations, combined with observations on young corpuscles, incline me 
to the view that the ring may rather be the consequence than the mechanical cause 
of the shape of the corpuscle, but the matter will come up for discussion again in the 
second part of these studies, when I am in the position to deal with the histogenesis of | 
the cells.* 
The question here arises whether the corpuscles which have assumed the biconvex 
disc shape are capable of division. Besides the corpuscles with oval nuclei, there are — 
others with round nuclei, and a smaller cell body showing a finer reticular structure. 
These do not assume the disc shape, though they are oval in form. They are found in — 
active division. In the second part of this memoir I shall discuss the relationship | 
between these two forms. Meantime it has to be determined whether both classes of 
cells are dividing elements. In the later stages of mitosis there is little to distinguish 
the one class from the other, for all dividing corpuscles are spherical. Variation in 
the size of the chromosomes would indicate a derivation from a coarser or finer 
chromatin network, and the round-nucleated corpuscles have distinctly a finer network 
of chromatin than those with oval nuclei. Direct observation, however, shows that by 
far the greater number of nuclei showing prophase stages are oval in shape, and between 
* MuvES, in a recent paper cited in the note to page 293, concludes that the band is the cause of the biconvex 
shape of the corpuscle. His explanation of the mechanism does not seem to apply very satisfactorily to the Lepidosiren 
corpuscles, but I must postpone a discussion of the question until all the stages in their histogenesis have been worked 
out. It seems to me that it is only by a study of the developmental stages that the significance of the band or ring can 
be determined. 
