DAVENPORT: PROCESSES CONCERNED IN ONTOGENY. 175 
the protoplasmie bodies in which they occur. These exist either as 
(1.) isolated cells, or as larger multinucleated bodies. Of the latter we 
may recognize three classes: (IL) bodies extended chiefly in one direc- 
tion, — threads, fibres, tubules; (ILI.) those which extend as a layer; 
and (IV.) those in which the three dimensions are more nearly equal, 
forming solid masses. 
I propose now to discuss the processes occurring in each of these four 
classes? 
I. ONTOGENETIC PROCESSES OCOURRING IN MIGRATORY PROTOPLASMIO 
30D1ES— MESENCHYME,? 
1. Migration of Nodal Thickenings in a Protoplasmic Mesh-work. This 
process is found, for example, in 
many Arthropod eggs before the for- 
mation of the peripheral blastoderm. 
(Figure 1.) No one can doubt that 
protoplasm extends throughout the 
whole egg in the form ot a mesh- 
or foam-work, whose interspaces are 
filled with yolk. The protoplasm 
is aggregated around the nuclei at 
certain nodal points, which later 
migrate to the surface or through 
the yolk as vitellophags. Cf. K. 
d H.’ Figs, 7, 363, 417, 448, 472, Tai 
473, 771. 
1 It may be a cause of dissatisfaction to some that this classification is not 
’; it is still more serious that the different heads are not of 
“strictly dichotomous’ 
co-ordinate rank or mutually exclusive. Of course, the classification employed in 
a final one. I hope, however, that I have succeeded 
this list cannot be regarded as 
in an attempt roughly to arrange the different items in a logical fashion. 
' is used as a name for all amo- 
2 In the present paper the word “ mesenchyme’ 
boid, migrating cells, of whatever origin. 
9 Throughout this paper certain abbreviations are used in referring to the books 
from which the figures are copied. These are: K. € H. for Korschelt und Heider's 
“ Entwicklungsgeschiehte " ; M. for Minot’s “ Human Embryology " ; and H.-M. for 
Hertwig's “Text-Book of Embryology of Man and Mammals,” translated by Mark. 
Fig. 1. Section through an egg of a Myriapod (Geophilus), showing the nodal 
thickenings (n. t.) in the act of migrating towards the periphery of the egg. See 
K. & H., Fig. 449. 
