﻿ix, d. 4 Cowles: Palaemons of the Philippine Islands 339 



who is not familiar with palaemons that the old males are of 

 the same species as the young males and females. The fol- 

 lowing are my reasons for considering the large brownish pa- 

 laemon, which is seen in our museums and sometimes in our 

 markets and which has the extremely long and thick chelipeds, 

 as the same species (P. carcinus) as the beautifully colored young 

 males and females with short weak chelipeds: 



1. Both the first and second antennae show the deep peacock blue color, 



which is found in no other species in our collection. 



2. If we assume that the large brown form with the enormous chelipeds 



is a different species from the smaller brightly colored males and 

 females, then we have to account for the facts that all of the large 

 brown forms are males, that no females have been found corre- 

 sponding to them in size and shape, and that the fishermen have never 

 caught any females like them. 



3. The number of teeth on the dorsal and ventral borders of the rostrum 



is approximately the same in both. 



4. While the rostrum is distinctly shorter proportionately in the large brown 



form, a gradual reduction in the relative length of the rostrum can be 

 traced if we place both kinds together in a series arranged according 

 to increasing body length. 



5. In living specimens a series shows how the brilliant color of the young 



gradually grades into the dull brown of the old form. 



6. Both kinds have the coat of felted hair on the mobile finger. 



7. The chelipeds are blue in both forms, but very dark blue in the large 



form. 



"Males feminises." — It is not possible to determine whether or 

 not our collection of P. carcinus contains what Coutiere 20 speaks 

 of as "males feminises," although all the males, except the oldest 

 ones, show the female characteristics; that is, the chelipeds 

 are weak and short. Plate I, figs, le and 1/, shows how little 

 the chelipeds of the full-grown female and the chelipeds of 

 the young male differ from one another. As a matter of fact, our 

 collection does not contain any young male which has taken on 

 the characteristics of the old males, with the possible exception 

 of the specimen (240 millimeters) noted in Table I. These 

 males are more numerous in our collection of Palaemon philip- 

 pinensis sp. nov., which is described on page 340. 



The enormous increase in the size of the chelipeds and the 

 change in shape of the fingers in the old males of P. carcinus, 

 P. lar, P. jamaicensis, and other species are phenomena which 

 cannot fail to stimulate the mind of the zoologist. Ortmann 21 

 thinks that we have every reason for believing that the beautiful 



'■"Ann. Sci. Nat., Zool. (1900), 11, 269. 



"' Bronn's Klassen und Ordnungen des Thier-Reichs (1901), 5, 1242. 



