14 Ji)urn,il of F,ntiiniiil()f:\ and Zonlo^jy 



cells reaching from the surface to the depths of the nervous system 

 and also probably bipolar sense cells as well as more or less deeply 

 placed multipolar nerve cells giving off fibers to the nerve areas. 



The epidermis is a general organ of sense, the exact nature of 

 which has not been very clearly determined. Spengel considers 

 that about the proboscis in its ventral face there are points espe- 

 cially sensitive. In fact at this place he describes a deep depression 

 which he regarded as a special sense organ. 



In the larval stage the first suggestion of a nervous system we 

 find in the development of the apical plate which in later stages 

 develops eye spots as simple caps of ectodermal cells surrounded by 

 pigment. The eye spots become anterior in position with a pocket 

 of the clear cells each ending in a point. Between the two eye- 

 cups a mass of pigment develops. At the base of the apical plate 

 nerve fibers begin to be seen. 



At metamorphosis in a region where the collar will develop a 

 transverse groove forms near the mid-dorsal line. In the mid- 

 dorsal region a strip of ectoderm not crossed by grooves makes the 

 beginning of the neural plate. It sinks beneath the surface and 

 folds of the adjacent ectoderm or neural folds meet over it, and in 

 this way the neural tube is formed. 



BIBL10GR.\PHY 

 Bateson, W. 



18?4. The Early Stages of the Development of Balanojrlossus. Q. Jour, 

 mic. sc, vol. 24, pp. 207-2.3.1, pi. 18-21. 



188."). Later Stages in the Development of Balanoglossus kovalevskyi. 

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1886. Continued account of the Later Stages in the Development of 

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1886. On the Morphology of the Enteropneusta. Stud. M. Z. vol. 3. pp. 

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 Davis, B. M. 



1908. The early Life History of Dolichoglossus pusillus. Univ. Calif. 

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DawydoflF, C. 



1909. Beobachtungen uber den Regenerationsprozess bei <len Rnterop- 

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 fig. P. 293 N. Syst. 



Haldeman. G. B. 



1886. Notes on Tornaria and Balanoglossus. J. Hopkins Univ. Circ. vol. 

 6, pp. 44-5. 



Herder, K. 



1909. Zur Entwickelung von Balanoglossus clnvigerus. Zool. aiiz. vol. 

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