REPORT OX TllK TUNTCATA. 



40 



In the lobes around the branchial aperture in Doliolum, in Sal pa, and probably in 

 other forms also, there are certain modified ectodermal cells, which appear to be nerve- 

 endings. They have filamentous processes which extend to the surface, and these have 

 probably a tactile function. 



In Pyrosoma there is a visual organ formed of an outgrowth from the nerve ganglion, 

 covered with pigment and having a refracting body imbedded in it ; and in Salpa there 

 is a similar organ also placed upon the ganglion. 



Tlie Neural Gland and Duct (The Hypophysial Gland, the Olfactory Gland). 



Underneath the nerve ganglion, and imbedded in the innermost layer of the mantle, 

 lies a gland first noticed by Hancock in 1868, afterwards more fully examined by Ussow 



Fir:. 10. — Diagrammatic transverse section through the dorsal region of the anterior end of a Simple Ascidian. 

 '..test; ec. , ectoderm ; n.g., nerve ganglion; m., muscle bands; U.S., blood sinus; gl., subneural gland; gl.d., duct of the gland: 



br.s.e., epithelium lining the branchial sac ; e.g. epibranchial groove. 



and Nassonoff (who first demonstrated its glandular nature), and brought prominently into 

 notice lately by Julin. 1 According to this author the neural gland corresponds to the 

 pituitary gland of the vertebrate brain, and retains by means of its duct, to be presently 

 described, that primitive connection with the pharynx which is lost in higher forms. 



In structure it is a tubular ramified gland (fig. 10 gl.) having a number of caecal 

 tubes lined by cubical epithelium, and surrounded by connective tissue containing a very 

 large number of blood sinuses. The caeca all converge towards the ventral surface of 



1 Julin, Arch. <le Biologie, t. ii. p. 59, 1881. 



(ZOOL. CHALL. EXP. — TART XVII. — 1S82.) 



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