396 CHARLES H. SPURGEON. 



EXPLANATION OF FIGURES AND ABBREVIATIONS. 

 The tissue was fixed with Perenyi's fluid . The sections from which the drawings 

 and photomicrographs were made were cut eight microns in thickness and stained 

 with Haidenhain's iron haematoxylin. The drawings were made with the aid of a 

 camera lucida. 



bm., basement membrane. opt. g. /.. optic ganghon fibers. 



br., bram. ^pt. n., optic nerve, 



c, cornea. o^^ ^^^ ^p^j^, (.^.^^^.^ 



cc, crystalline cone. pg, c., pigment cell. 



eg., corneagen cell. yg_^ retina. 



con., connective tissue. ret., retinulse. 



cu., cuticula. yi^a., rhabdom. 



hy. c, hypodermal cells. sec. th., secondary thickenings of the 



mils., muscle. hypodermis. 



opt. g., optic ganglion. j.., vitrella. 



Photomicrograph A. Horizontal section of the eyes of C. setosus. 



Photomicrographs B and C. Horizontal sections of the eyes of C. setosus. 

 C has the cuticula removed. The cuticula in B is thinner in the retinal than it is 

 on the sides of the optic stalk. It is not as thick as it appears to be in the retinal 

 region, due to the fact that it is wrinkled. It is also pulled loose from the under- 

 lying hypodermis, caused by the shrinking of the more delicate tissues. 



Photomicrograph D. Horizontal section of the brain of C. setosus. 



Photomicrographs E and F. Horizontal sections of the eyes of C. pellucidus. 

 The cuticula has been removed. F has a tract of nerve fibers extending anterio- 

 medianly towards the hypodermis, but there is no thickened portion of the hypo- 

 dermis with which it is connected. 



