Parker. — Blind Crayfishes. 



EXPLAXATIOX OF FIGURES. 



ABBREVIATIONS. 



The specimens from which the following figures were talcen were killed and 

 preserved in strong alcoliol, and stained in Czoclier's alum-cochineal. The cray- 

 fish from the optic stalk of which Figure 1 was drawn was 6 cm. long. That from 

 which the remaining figures were made was 4.4 cm. long. 



Fig. 1. A longitudinal horizontal section through the right optic stalk of Cam- 

 barus setosus, Fa.xon. The liistological detail is "^iven in the hy- 

 podermis only. The optic ganglion and the optic nerve are tinted. 

 Between these structures and the hypodermis tlie space is filled with 

 a loose connective tissue. X Go. 



" 2. A longitudinal horizontal section tlirough the right optic stalk of Cam- 

 barus pellucidus, Tellk. This drawing was made in the same manner 

 as Figure 1. X 65. 



" 3. An enlarged drawing from the distal end of the section which immediately 

 follows that from which Figure 2 is taken. This figure shows the details 

 in the retinal enlargement of the hypodermis. The space between 

 this enlargement and the cuticula was artificially produced. X 275. 



" 4. Tangential section of the hypodermis from the side of an optic stalk of 

 Cambarus pellucidus. X 275. 



" 5. Tangential section of the superficial portion of the retinal thickening in 

 the eye of Cambarus pellucidus. X 275. 



" 6. Tangential section of the deep portion in the retinal thickening of the eye 

 of Cambarus pellucidus. This section is taken from the same series 

 as the one from which Figure 5 was drawn. X 275. 



