DAVENPORT: PROCESSES CONCERNED IN ONTOGENY. 195 
Saeculina, where the thorax and abdomen are throwu off, the head alone 
) 2 
persisting to complete the metamorphosis. 
Fic. 30. 
6. Another division process is that of splitting of the mass. This is 
illustrated by the case of the optic mass 
of the lobster (Figure 30), which splits 
into an outer and an inner part. Com- 
pare the origin of the nervous system of 
Peripatus, K. & H., Fig. 442, B. 
7. Under the second head, fusion of 
contiguous masses, we may place such 
oes as that of the union of indepen- 
dently arisen ganglionie masses, such as 
z f ventral 
Morgan deseribes for the Pantopod, Pal- gongia. 
lene (Figure 31). Fio. 81. 
Fig. 80. Sections through three stages in the development of the compound 
eye of the lobster after G. H. Parker. In Band C the mass is seen to be splitting 
into the retina and optic ganglion. See K. & H., Fig, 263. 
Fig. 31. Ventral part of sections across Pallene embryos. A, earlier stage, 
showing the paired neural invaginations ; B, later stage, ganglia fused. See K. & H., 
Figs. 409, 410. 
