i 9 8 THE TANGANYIKA PROBLEM. 



specimen, collected by Canon Tristram in the same lake. But these eggs, produced 

 by fishes of the size of our common perch, are very numerous, and measure only about 

 2 millim- in diameter. It has, besides, been observed in these Tilapia, as well as 

 in the Siluroids, that the function of protecting the eggs devolves on the male sex, 

 while, to my surprise, the Tanganyika fish proved on autopsy to be a female. 

 Whether this is constantly so, or whether either parent takes to the nursing duties, 

 remains to be ascertained by examination of a larger number of specimens. I am 

 all the more disposed to think the latter possibility will be confirmed, from the fact 

 that a specimen of Tilapia nilotica with the pharynx filled with embryos belongs 

 to the female sex, while Dr. Lortet's observations on T. simonis had led to the belief 

 that specimens carrying eggs in that manner are invariably males. 



It is here necessary to recall the observation contained in Livingstone's " Last 

 Journals" (vol. ii. p. 17), that the " Dagala " or "Nsipe" of Lake Tanganyika, a 

 small fish two or three inches long and very like whitebait, is said to emit eggs by 

 the mouth. The comparison of this fish to whitebait excludes the possibility of the 

 one here described being the " Dagala " or " Nsipe," which will probably prove to 

 be a Cyprinodont, if not actually the Haplochilus taiiganicaniis described below. 



65. Tropheus annectens. — Blgr. 1900. 



66. SlMOCHROMIS DIAGRAMMA. Gthr. 1 893. 



67. Tilapia nilotica. — L. 1757. 



68. Tilapia burtoni. — Gthr. 1893. 



69. Tilapia horii. — Gthr. 1893. 



70. Tilapia rubro punctata. — Blgr. 1899. (Fig. facing p. 204.) 



Teeth very small, in 4 or 5 series in both jaws, outer bicuspid, separated 

 from the series of smaller tricuspid teeth by a rather wide interspace. Depth of 

 body 3 times in total length, length of head 2§. Snout, with straight upper 

 profile, twice as long as diameter of eye, which is 4^ times in length of head 

 and equals interorbital width ; mouth large, \ width of head, extending to between 

 nostril and eye ; a few deciduous scales on the cheek ; large scales on the opercle. 

 Gill-rakers short, rather slender, 12 or 13 on lower part of anterior arch. Dorsal 

 XVI. 9 ; spines equal in length from the sixth or seventh, measuring 5 length of 

 head and | longest soft rays. Pectoral obtusely pointed, f length of head, not 

 extending to origin of anal. Ventral reaching vent. Anal III. 7 ; third spine 

 a little shorter than longest dorsals. Caudal truncate. Caudal peduncle as long as 

 deep. Scales mostly cycloid, a few on the sides of the body below the lateral line 



4 — 5 22 



finely denticulate, 32-33 - ; lat. 1. . Olive-brown above, pale yellow 



3 ° JJ 11 — 12 12 — 13 r 



beneath ; dark cross-bars on the back ; each scale of the back and sides with a 



central vermilion spot ; head spotted and marbled with dark purplish brown ; lower 



jaw and lower part of opercular region bright yellow ; dorsal and caudal fins bright 



