866 



SCIENCE 



[N. S. Vol. XXXIII. No. 857 



described the scales of Alhula, showing that 

 they have much in common -with those of 

 Amia, and are very different from those of 

 Elops. The Albulidse are evidently much 

 nearer to the Cycloganoidei than are the 

 Elopidse, and if these two families stand side 

 by side in the system, it must be understood 

 that they are nevertheless quite far apart in 

 fact. The striking feature of the scales in 

 which Albula resembles Amia is the entirely 

 longitudinal (instead of transverse) arrange- 

 ment of the basal circuli, which in fact should 

 be called fibrillos. In Amia the nucleus is 

 subapical, and the broad nuclear area is rugu- 

 lose or covered with fine labyrinthiform mark- 

 ings. All this is seen in the living Amia 

 calva, but even more beautifully in the Mio- 

 cene Amia scutata Cope, scales of which I 

 obtained at Florissant last month. Cope 

 states that the scales of A. scutata are larger 

 than those of A. calva, but I find them to be 

 practically of the same size, with very strong 

 longitudinal fibrillas, fraying out basally, and 

 a most beautiful and intricate labyrinthiform 

 sculpture in the broad nuclear area. This 

 labyrinthiform condition of the nuclear area 

 is not uncommon among the lower groups of 

 teleosteans in the stricter sense, and is vari- 

 ably developed in Elops. In the characinid 

 Prochilodus rubrotceniatus Schomb. the tran- 

 sition from the rugose or labyrinthiform nu- 

 clear area to the regularly circulate type is 

 curiously shown, the area becoming multi- 

 nucleate, with several small " islands " sur- 

 rounded by circuli. Albula vulpes has large 

 subquadrate scales, with about three basal 

 radii, leading to deep emarginations of the 

 base, which therein departs markedly from 

 Amia and resembles the normal condition of 

 many higher Teleosts. The subapical region 

 is rugulose, very much as in Amia, but the 

 true nucleus, just below it, is surrounded by 

 fine regular circuli. It is in this small central 

 region, above the nucleus, that Albula has 

 genuinely transverse (concentric) circuli. It 

 is also to be remarked that the basal circuli 

 are all beaded in Albula, whereby they differ 

 from Amia, but agree with the Osteoglossidse. 

 Strong new interest in the Albulidse has 



been aroused by the description of a new 

 genus by Mr. Henry W. Fowler in Proc. Acad. 

 Nat. Sci. Philadelphia, LXII. (1911), p. 651. 

 This very interesting fish, Dixonina nemop- 

 tera, was found mixed with specimens of 

 Albula from Santo Domingo, collected long 

 ago by Gabb. Fowler writes of the scales 

 that they are " cycoid, inner edges mostly 

 crimped, outer or exposed edges thin or mem- 

 branous and ragged, marked submarginally 

 with a concurrent vertical ridge or striation, 

 the true edge of the scale." I am greatly in- 

 debted to Dr. D. S. Jordan for an opportunity 

 to study a couple of scales of Dixonina nem- 

 optera, taken from the original type. They 

 are about 8.5 mm. broad and long, and in 

 structure agree perfectly with those of Albula. 

 The nucleus with its concentric circuli, the 

 beaded longitudinal basal circuli, the three 

 basal radii and three basal emarginations, etc., 

 are all the same. The dermal pigment spots 

 also agree. In some ways this exact corre- 

 spondence is rather disappointing, but it 

 shows the conservative nature of the scale- 

 pattern, and rather emphasizes its value as 

 diagnostic not merely of the genus Albula, 

 but of the group to which it belongs. 



t. d. a. cockerell 

 Univeksity of Colorado, — -- 

 BouLDEB, Colo. 



THE SIGNIFICANCE OF LEAD ARSENATE COMPOSITION 



The control of a large class of the insect 

 pests of growing crops depends on the use of 

 arsenical sprays, and the commercial impor- 

 tance of such spraying has assumed very large 

 proportions in recent years. Two factors de- 

 termine the limits to which such methods 

 may be carried with success. The first factor 

 is the amount, character and timing of the 

 applications necessary to control the insect. 

 The second factor is the degree of toleration 

 for the spraying treatments which the crop in 

 question may possess. It is with the latter 

 part of the problem that the following dis- 

 cussion is concerned. 



Arsenic may injure plants quite as seriously 

 as animal tissue, and the efforts of investiga- 

 tors have been directed towards preventing 



