No. I.] PECTORAL APPENDAGES OF PRIONOTUS. 1 87 



Historical. 



Dr. Harrison Allen (11) found four layers of epidermal cells 

 in P. palviipes, but does not describe the modifications which 

 arise in the epidermis over the surface of the papillae, and does 

 not describe the manner of the nerve endings. 



As already noted, the Triglidae have received considerable 

 attention from European anatomists. In 1808 Samuel Collins 

 discovered the enlargements on the spinal cord, and in 181 1 

 Tiedeman (12) observed that the free rays were in some way 

 related to the spinal enlargements. The latter also described 

 and figured the musculature of the free rays. 



Deslongchamp, who was the first to observe these fish in 

 captivity, claimed that the free rays were organs of locomotion. 

 Tiedeman (12) records having seen a Trigla move on the deck 

 of a ship by means of the free rays. 



The muscles of the free rays were carefully studied by Des- 

 longchamp, and later by Jobert (2). The latter states that 

 there are many anomalies. 



Jobert (2) concludes that the free rays are modified fin rays. 



The cross sections of the free ray of Trigla, as shown by 

 Jobert (2) and Zincone (3), are elliptical, with the antero-pos- 

 terior diameter nearly twice as great as the one at right angles 

 to it. The general arrangement of the axial skeleton nerves 

 and blood vessels is essentially the same as in Prionotiis. No 

 detailed drawings of the epidermis are given. 



From the descriptions given by Jourdan (4), Jobert (2), and 

 Zincone (3), the epidermis of the free rays of Trigla resembles 

 that in Peristedioji more than that in Prionotiis. 



There is a sub-epidermal nerve plexus as in Prionotiis. Mer- 

 kel (i) was able to trace the nerve fibers into the epidermis, 

 but could not follow them. Jobert (2) by the use of gold chlo- 

 ride, found each fiber connected with a small terminal body 

 (corps epidermique) in the epidermis which measured .004 to 

 .005 mm. in diameter. Zincone {3) claims to have found nerve 

 fibers continuous with spindle-shaped cells. 



Jourdan (4) found the non-medullated nerve fibers of the 

 free rays of Peristedion terminating in small papillae on the 



