94 ERNEST WARREN. 



EXPLANATION OF PLATES X AND XI, 



Illustrating Dr. Ernest Warren\s paper "On Tubularia 

 solitaria sp. nov., a Hydroid from the Natal Coast." 



Fig. 1. — Natural size. A group of hydi-oicls attached to a white 

 siliceous sponge. 



Fig. 2. — x 5. Somewhat enlarged view of a specimen attached to 

 sponge. 



Fig. 3. — X 5. Six specimens showing the variable extent to which 

 the hydrocaulus is imbedded in the sponge, and also the variable 

 character of the hydrorhiza. 



Fig. 3 a. — X 10. A specimen in which the hydranth has shrivelled 

 away or dropped off. 



Fig. 4. — x 25. Enlarged drawing of side view of specimen. Notice 

 the ridges on the hypostome, which are the continuations of the oral 

 tentacles ; the gonophores arising in clusters from semi-erect peduncles, 

 which spring just above the verticil of basal tentacles ; the longitudinal 

 banding, which is more particularly obvious over the middle region of 

 the hydrocaiilus, due to the i^resence of the endodermal canals ; a thin 

 '■ rootlet " (>•) on the right of the hydrocaulus, and a thick '" tuber " filled 

 with reserve food on the left. 



Fig. 5. — x 75. — Longitudinal vertical section of hydranth and upper 

 portion of stem. Notice : longitudinal ridge of hypostome projecting 

 down as a lobe (J.) into digestive cavity ,- base of hydranth occupied by 

 endoderm, consisting of (1) liasal endodermal epithelium (b. ep.) ; (2) 

 reticular layer of vesicular endoderm ; (3) smaller endoderm cells lying 

 next to the mesoglea (6. ed.) ; diaphragm {d.) with an endodermal epi- 

 thelium [ed.) on one side and a vertical septum (r. s.) on the other ; 

 perisarc groove {j>. g.). 



Fig. 5 a. — x 300. Basal epithelium from the floor of the digestive 

 cavity of hydranth. It consists of amoeboid cells enclosing masses of 

 apparently worked-up food material (p. r.) and of glandular cells. 



Fig. 6. — x 300. Perisarc-secreting groove showing the production 

 of the perisarc (p). 



Fig. 7. — X 300. Hypostome endoderm with the secreting cells, which 

 stain intensely. Such are usually found in the hypostome of the hydroid- 

 polyp. 



Fig. 8. — x 300. — Cross section of hypostome region ; it shows the 

 absence of ectoderm over the contact-plane of the tentacular ridge. 



