115 



«3qttatic ILitt 



larly in males, we find a metallic blue 

 spot on the sides. 



I have gone minutely into the charac- 

 teristics of the hybrids in order to bring 

 out clearly the dominant colors and to 

 show that it is not at all strange that 

 black should prevail. In well colored 

 specimens of the black (nigra) form of 

 P. maculatus the body is all black except 

 the back and belly, the sides overlaid 

 with bright metallic blue. If so intense 

 a black is found in this variant relative, 

 it is small wonder that the hybrids, with 

 black showing in both parental species, 

 should be thus darkly marked. 



Males of the cross have well developed 

 but short spikes to the tails, showing the 

 helleri blood. Many of the spikes are 

 orange, while the entire tail may be sim- 

 ilarly tinted. The other fins are generally 

 clear. In size the hybrids are about mid- 

 way between the parents. They are in- 

 clined to be shy, resembling X. Helleri 

 in this respect. In this hybrid we have a 

 form which in all respects is a composite, 

 showing some of the characteristics of 

 each parent, but differing from both in 

 that both sexes are of the same size and 

 general coloration, with the sex ratio 

 reversed. 



It is well to note that in the hybrids 

 there is little or no change in color from 

 birth to maturity as there is in both par- 

 ents, for in pure bred types the young at 

 birth are all olivaceous in color, putting 

 on the more brilliant hues only when 

 mature. 



On account of lack of tank space I 

 was unable to segregate any particular 

 pairs of ibis first generation of hybrids 

 to breed from, but was obliged to keep 

 all the composite types in one large tank. 

 I am unable, consequently, to say what 

 line ln-eeding would have had on 

 the next generation. Early in September, 

 [QiQ, 1 noticed the first young of the sec- 



ond hybrid generation. They were ex- 

 pelled a few at a time, usually not more 

 than 8 or io, which is rather at variance 

 with the parental species which may pro- 

 duce large litters within a few hours — 8o 

 for helleri and 40 to 50 for maculatus be- 

 ing not uncommon. 



Out of a total of 310 young of this 

 second generation, 29.4 per cent., or, to 

 be exact, 91 individuals, reverted back 

 to the original types. Three were macu- 

 latus rubra (2 males, 1 female), and of 

 the 88, 40 per cent, were helleri rachovii 

 and 60 per cent, typical helleri. All ap- 

 peared to be dwarfs, not reaching half 

 the size of those of the composite group, 

 but small as they were the females show- 

 ed a tendency to be larger than the males, 

 and as close as could be determined there 

 were four times as many females as 

 males ; thus in these throw-backs we see 

 the characteristics of the original species. 



In the 219 composite fish we find for 

 the most part the intense black predomi- 

 nating, but on the other hand the red, 

 when it appears, is much more intense, 

 not an orange or sandy red as in the first 

 hybrid generation. There were also more 

 speckled fish than in the first generation, 

 which were blotched rather than speckled. 

 Many are solid bright red forward from 

 the dorsal fin with the remainder of the 

 body intense black, including dorsal and 

 tail, and reminding one very much of a 

 black male of Gambusia affinis; some 

 are light red with vertical markings of 

 black, and the general color scheme is 

 much more diverse than in the previous 

 generation. Thus far the sexes are about 

 equal in size and color, except, that the 

 red is lighter in the females, often sandy. 

 These hsh are developing much more 

 rapidly than the first generation under 

 exactly the same conditions. It is not yet 

 possible to determine the ratio of the 

 sexes. 



( Concluded on page t t 7 ) 



