596 



A. WILLEY. 



confused topographical with morphological conceptions in 

 regard to the organ of fixation in the larva of Ciona intes- 



FiG. 7. — Diagrams of an Eutero|)neust (A), an Ascidian larva (B), 

 and a Craniate embryo (C). After Willey ('Zoological Results,' 

 part vi, 1902), by permission of the Cambridge University Press. 



A. — •/;. Proboscis, p.p.c. Proboscis pore-canal opening externally 

 close to the anterior neuropore. c.v. Collar nerve-tube. ep. Epi- 

 physial roots, s. Stomochord. m. Mouth, c. Collar region, g. 

 Gut. t. Trunk region, dji.t. Dorsal nerve tract, a. Anus. py. 

 Pygocliord. 



B.— /.o. Organ of fixation, e. Endostyle. m. Mouth, a.v.c. 

 Anterior nenrenteric canal, s.n.g. Subiieural gland, c.v. Cerebral 

 vesicle, sp. Medullary tube. pn.c. Posterior neurenteric canal. 

 n. Notochord. 



C. — ep. Epiphysis cerebri or pineal organ, f.b., m.h., and h.b. 

 Fore-, mid-, and hind-brain, hy. Hypophysis cerebri. ///. Thyroid 

 gland. Other letters as above. 



