A CONTRIBUTION TO THE MORPHOLOGY OF 



THE VERTEBRATE HEAD, BASED ON A 



STUDY OF ACANTHI AS VULGARIS. 



JULIA B. PLATT. 



These studies, begun under the direction of Dr. C. O. Whit- 

 man, were completed in the summer of 1890, at the Marine 

 Biological Laboratory of Wood's Holl. I acknowledge grate- 

 fully the valuable criticism and suggestion with which Dr. 

 Whitman has followed my work. 



My material consisted of nearly a thousand specimens, col- 

 lected on the coast of Massachusetts at Lanesville and North 

 Truro. Among the hardening reagents employed, picro-sul- 

 phuric acid proved the most reliable. However, specimens 

 hardened in Perenyi's fluid were also good, while osmic acid 

 and gold chloride have given some valuable results. For dif- 

 ferentiation the common hematoxylin and carmine stains were 

 used. The reconstructions, showing the development of the eye- 

 muscles, were obtained from series of camera outlines, which 

 were projected on paper ruled to a scale corresponding to the 

 magnification of the drawings, and to the thickness of the 

 sections from which they were taken. The flat projections 

 thus obtained were then shaded in order to represent more 

 clearly the relative depth of different parts. By these recon- 

 structions I have endeavored to give a definite idea of the 

 successive changes through which the head cavities pass in the 

 process of transformation. Although the final results do not 

 differ from those obtained by Van Wijhe (No. 16) nearly ten 

 years ago, it is hoped that a more complete presentation of the 

 steps by which these results are reached may not be devoid of 

 interest. The scientific value of an exact knowledge of the 

 position in which the eye-muscles arise is sufficiently evinced 

 by the stress which Rabl (No. 15) lays upon the location of 

 the primary somatic muscles, as determining, to a degree, 

 the homologies of head and body somites. 



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