EXPLANATIONS OF PLATES 



ABBREVIATIONS 



ad.p., adhesive papilla 



at., atrium 



at.s., atrial siphon 



ch., chorion 



e, eye 



en., endostyle 



end. sd., endodermal strand 



g., definitive ganglion 



g.o., gill opening 



ht., heart 



hyp., hypophysial duct 



int., intestine 



k., keel 



I., lens 



Ix., lens cell 



m., mantle 



mc, muscle cell 



m.f., muscle fibrilla 



mes., mesenchyme 



n, notocord 



n.c, neural canal 



n.cd., nerve cord 

 o.s. oral siphon 

 per, pericardium 

 ph., pharynx 

 pg, pigment cup 

 r., rectum 

 r.c, retinal cell 

 ret, retina 



sn. g., subneural gland 

 St., stomach 

 Stat., static organ 

 S.V., sensory vesicle 

 t., tail 



t.c, test cell 

 t.f., tail fin 

 tu., tunic 

 t.ves., test vesicle 

 v.g., visceral ganglion 

 v.n., visceral nerve 

 vis.rd, visual rod 

 y., yolk mass 



With the exception of figure 1, which was drawn by Miss Besse E. Stocking, 

 the drawings have been made by the writer of the paper, camera lucida outlines 

 forming the basis for each. Figures 2 and 4 illustrate structures of the 

 embryo, all others are of the free-swimming tadpole larva of Amaroucium con- 

 stellatum. Text figure A taken from a paper by the author published in The 

 Journal of Experimental Zoology, volume 30, number 2, February 20, 1920, 

 page 243. 



ABBREVIATIONS TEXT FIGURE A 



as, atrial siphon 



dap, dorsal adhesive papilla 



L, left side 



Ipo, light perceiving organ 



map, middle adhesive papilla 



Mc, muscle-cell sheath 



n, notocord 



OS, oral siphon 



R, right side 



sc, statolith cell 



sv, sensory vesicle 



tf, tail fin 



tg, groove in test resulting from 

 pressure of the tail during em- 

 bryonic development 



tv, test vesicles 



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