BROOKS AND RITTENHOUSE: ON TURRITOPSIS. 433 
Part 2. Notes on the Anatomy and Systematic Affinity 
* of Turritopsis. 
By William Keith Brooks and Samuel Rittenhouse. 
(With plates 30-32. The references in Part 2 and Part 3 are to the 
illustrations that accompany this paper. Of these, plate 30, figure 4, and 
plate 31, figure 8, were drawn by W. K. Brooks, and the remaining figures 
by Samuel Rittenhouse.) 
I The illustrations of the adult Turritopsis in the memoir of 1886 are 
too small to show the anatomical details, and they are now supple¬ 
mented by an enlarged figure of the adult (pi. 30, fig. 4), which was 
drawn from a living specimen by W. K. Brooks at Beaufort, North 
Carolina, in 1885; and by the illustrations of sections by Samuel 
Rittenhouse in plates 30 and 31. 
As figure 4 of plate 30 shows, the radiating canal is bent upon itself 
twice, at right angles, and consists of four sharply defined regions: 
an ascending region which arises from the stomach, a horizontal region, 
a descending region which ends in the circular marginal canal, and a 
blind diverticulum which is a continuation of the ascending region. 
Plate 30, figure 1, is a section through the plane of the middle of the 
reproductive organs in figure 4. It shows that the radial canal arises 
from the stomach as a groove or channel that consists of prismatic 
transparent endoderm cells with conspicuous cell walls. As figure 4 
shows, the channel arises from the stomach in the plane of the oral 
ends of the reproductive organs and remains an open groove as far 
as the plane of the aboral border of these organs, gradually deepening 
and infolding until it becomes converted into a tube as is shown in 
plate 30, figure 2. This is a section through a plane that is just above 
the reproductive organs. The endoderm cells are now chorda cells 
with conspicuous cell walls and transparent contents. The four 
radiating tubes meet each other and are flattened by pressure over 
the areas of contact, where the ectoderm is absent, so that the endo¬ 
derm of one tube is separated from that of adjacent ones by the sup¬ 
porting layer only. In the center is a square area lined with the 
ectoderm of the subumbrella, and occupied by the jelly of the umbrella. 
The convex peripheral portion of each tube is covered with ectoderm. 
The distribution of the ectoderm will be understood by reference to 
i 
