Aquatic Hifc 



114 



lemon-yellow stripe above and below, it 

 and with bright yellow or orange in the 

 tail. 



In 191 5 I mated a particularly large 

 and highly colored male of X. helleri to 

 a correspondingly well developed female 

 of the same species belonging to the 

 phase called "rachovii." From their 

 progeny I paired the best female, with 

 strong rachovii characteristics, to an un- 

 related male of the bright red type. From 

 this union I selected what promised to 

 be a fine "rachovii" female and bred her 

 to a deep red male of Platypqecilus mac- 

 ulatus {rubra). 



In November, 1918, I was rewarded 

 with two litters of hybrids, 98 in all. Six 

 of the fry were "throw-backs," and were 

 to all appearances straight females of 

 P. maculatus, of a pale sandy color ; of 

 the 92 composite individuals there were 

 but twenty females, but all, both sexes, 

 were darkly mottled over the entire body 

 from birth. Let us digress for a moment 

 for a comment on the preponderance of 

 males. With X. helleri, its form "racho- 

 vii, and Platypoecilus maculatus, pure 

 litters usually contain more females than 

 males, generally in the ratio of 8 or 10 

 to I ; in the hybrids, you will note, this 

 tendency is reversed, but not in quite the 

 same ratio. 



The hybrids, both male and female, 

 rather favor the maternal parent in 

 shape, and both sexes are practically of 

 the same size and color, although the red- 

 dish hues in the male hybrid are straw 

 color in the female. In this connection 

 note the departure from the parental 

 forms wherein the females are much 

 larger than the males and are almost 

 entirely lacking in any of the brilliant 

 colors so characteristic of males. In 

 many of the hybrids the scales are over- 

 cast with dark blue, like blued steel, 

 similar to that seen in a well colored male 

 of the "nigra" form of P. maculatus. A 



peculiarity of the color scheme is that 

 black predominates and is confined al- 

 most entirely to the posterior portion >>\ 

 the body, forward of the dorsal being 

 red speckled with black. 



By a careful study of the colors in both 

 parent species we see the reason for the 

 excess of black, and why it is naturally 

 confined to the tail rather than the head. 

 In typical X. helleri there is a black bor- 



Platypoecilus maculatus 



Upper, male of red'phase (rubra); lower, female of black 

 phase (nigra) 



der, both edges, to the sword-like exten- 

 sion of the tail-fin ; in the form rachovii 

 there is in addition to the black border a 

 large crescent-shaped black spot at the 

 base of the tail ; in P. maculatus. red 

 form or "rubra," appears this same black 

 spot and males have small black dots 

 more or less over the entire body. It is 

 asserted, and we believe correctly, that 

 the forms of P. maculata called rubra, 

 nigra and pulchra are color variants de- 

 A r eloped by aquarists, and this species in 

 nature, as well as A', helleri, is much 

 given to color variation. Typical P. ma- 

 culatus is olivaceous in color shading to 

 pearly white on the belly. The dark 

 crescent or half-moon shaped spot at the 

 base of the tail is in evidence and in most 

 specimens a dark spot appears on each 

 side of the body. Occasionally, particu- 



