Mr Menon, Notes on Semper s Larvae. 417 



EXPLANATION OF PLATE IV. 



Fig. 1. Semper's first larva, x 5. 



Fig. 2. Neniatocysts of same. a. small x 330 ; b. large x 200. 



Fig. 3. Transverse section of same (diagrammatic). 1 — 6, first six 

 pairs of mesenteries. 



Fig. 4. Sterrogastrula of same, x 50. 



Fig. 5. Transverse section of 4. ec. ectoderm ; m. mesogloea ; 

 en. endoderm mass ; vac. vacuoles ; y. yolk. The cilia 

 of the ectoderm are not shown in this or in any of the 

 drawings. 



Fig. 6. Transverse section of a stage later than 4. Letters as 

 before, coel. coelenteron. 



Fig. 7. Longitudinal section of a still later stage. Letters as 

 before, stoni. stomoclaeum : mes. mesentery. 



Fig. 8. Youngest specimen of Semper's second larva, x 30. 



Fig. ( J. Neniatocysts of an older larva, a. small x 1000 ; b. large 

 nematocyst x 800. 



Fig. 10. Transverse section (diagrammatic) of 8. 1 — 3, mesenteries 

 (macro.). 



Figs. 11 and 12. Transverse sections of two later stages. 1 — 6, 

 the six pairs of mesenteries (macro, and micro.). 



