BROOKS AND RITTENHOUSE: ON TURRITOPSIS. 433 



PART 2. NOTES ox 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.) 



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 \V. 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 bv reference to 



