204 CARNEGIE INSTITUTION OF WASHINGTON. 



somes, act as catalysts to inhibit, modify, and in rarer cases to promote 

 development. The nature of genes should be sought in physico-chemical 

 investigations of blood and lymph in pedigree cultures; for, if chromosomes 

 are the vehicle of genes, blood and lymph are the media through which 

 they act in the control of development. In such studies the spectroscope 

 is likely to be found most useful. 



Preliminary experiments are being made in breeding Colias interior Scudder, 

 a subarctic species found in northern and north-central Canada and also in 

 the White Mountains only 50 miles north of the site of Dartmouth College 

 (Hanover, New Hampshire). 



Habits and Local Distribution of Tortugas Fishes, by W. H. Longley. 



Study of the habits and local distribution of fishes occurring at Tortugas 

 was continued with satisfactory results from June 7 till August 25, 1921. 

 During this time photographs were secured recording the appearance, alter- 

 native color-phases, or interesting activities of 25 species. 



In the course of more intensive effort than had been made hitherto to de- 

 termine with accuracy the distribution of local species in the shallow waters 

 of the atoll, nearly 30 were discovered with which the writer had no previous 

 acquaintance. Of these, 4 or 5 are perhaps new to science. The finding of 

 others at Tortugas greatly extends their range. Such is the case, for example, 

 with Prionodes baldwini (Evermann and Marsh), otherwise known only from 

 Porto Rico. loglossus calliurus (Bean), known hitherto only from the Pensa- 

 cola snapper-banks, where it has been found in the stomachs of other fishes, 

 belongs in the same class. It is rather common at Tortugas on a certain sort 

 of bottom covered with small fragments of dead coral. It is small, alert, in- 

 conspicuous in coloration, and never appears to go far from its burrow. It 

 is, therefore, well adapted to escape observation and capture by ordinary 

 methods. The adults commonly occur in pairs sharing the same burrow, 

 as do also sometimes as many as 7 or 8 small ones. The young have a 

 symmetrical bilobed caudal quite vmlike the lance-shaped fin of the adult. 



There is uncertainty at present regarding the relation to one another of the 

 different species of Eupomacentrus to be found in the West Indian region and 

 adjacent waters. The difficulty in classification appears to be due largely to 

 the fact that their coloration changes greatly with age, and also that they 

 possess (in common with perhaps the greater number of tropical reef-fishes) 

 powers of instantaneous reversible color-change. 



At Tortugas 4 species occur, or 5 if E. leucostidus (Muller and Troschel) 

 and E. analis (Poey) be not one, as observation indicates they are. The 

 others are E. fuscus (Cuvier and Valenciennes), E. planifrons (C. and V.), 

 and a black and white or dark brown and pale yellow species, which is ap- 

 parently E. partitus (Poey). The very young E. partitus has not been taken 

 at Tortugas; but while very small specimens of E. fuscus are rather rare during 

 the summer months, E. planifrons a centimeter or two in length is not un- 

 common, and E. leucostictus of the same size is abundant. The young E. 

 fuscus is brick-red antero-dorsally, otherwise dusk}^ except for a large ocellus on 

 the soft dorsal fin and another upon the dorsal surface of the caudal peduncle. 

 The young E. planifrons is yellow, with an ocellus on the soft dorsal, corre- 

 sponding to that of E. fuscus, and a conspicuous black spot on the dorsal 

 side of caudal peduncle, E. leucostictus is purple antero-dorsall}^, otherwise 

 yellow. It has a dorsal ocellus, and may or may not develop a spot upon the 

 caudal peduncle. 



A goby of the genus Gobiosoma almost invariably shares the burrow of a 

 species of shrimp which the latter makes in fine sand or mud. The fishes 



