THE HISTOLOGY OF THE BLOOD OF LARVA OF LEPIDOSIREN PARADOXA, 465 
This may be expressed in the following scheme :— 
Puase I. 
Primitive blood cells 
Primitive erythroblasts Primitive leucocytes 
Puase II. 
Mesenchyme cells 
Mononuclear cell Mononuclear cell 
rythsoblase Parhiat 
Young erythrocyte | Hyaline, Basophile, Painarphesale leucocyte | 
Mature ee | Granular cells in a their varieties | 
As I have already said, LacurssE adopts a scheme very closely similar to this, and 
the origin of both red and white corpuscles from a common mother cell in the blood 
was first suggested by Povcurr in 1879. ‘The same sort of scheme was set forth by 
Giext0-Tos in his account of hematogenesis in the adult lamprey. My large mononuclear 
mesenchyme cell would also represent the embryonic form of the parent white cell 
postulated by PappenHerIm as the forerunner of the erythroblast, while from an 
embryological point of view my results in a general way agree with those obtained 
by SaxeErR, according to whom the red cells in the mammalia are derived from 
polymorphic mesenchyme cells, while the leucocytes are derivatives of similar cells 
at a later stage of development. 
DESCRIPTION OF PLATES. 
All the drawings were carefully traced with Abbé’s drawing apparatus (Zeiss). The lenses used were 
the 3 mm. 1°40 N.A. apochromatic lens or the 4 mm. 0°95 N.A. apochromatic lens of Zeiss with com- 
pensating oculars 4, 6 or 8. The substage condenser was the achromatic combination 1:0 N.A. of Zeiss. 
The following lettering in the figures used to indicate the different catagories of free cells :— 
s.m., small mononuclear ; 7.m., large mononuclear ; 0.p., basophile polymorph ; g.p., granular poly- 
morph ; f.g.p., finely granular polymorph ; ¢.g.p., coarsely granular polymorph ; ery., erythro- 
blast. 
Puate I, 
Fig. 1. Group of free cells in a space between the mass of yolk cells (hy) and splanchnic mesepithelium 
(spm). x 500. Stage 26. Som., somatopleure. 
Fig. 2. Primitive yoke-laden blood corpuscle from heart tube; safranin, Stage 26. x 800, 
