TI1E TANGANYIKA PROBLEM. 
9 s 
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 Tila/>i<e, 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 7 'ilapia nilotica with the pharynx filled with embryos belongs 
to the female sex, while Dr. Lortet’s observations on T. si /non is 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 tanganicanus described below. 
65. Tropheus annectens. — Blgr. 1900. 
66. SlMOCHROMIS DIAGRAMMA. — Gthr. I 893. 
67. Tilapia nilotica. — L. 1757. 
68. Tilapia burtoni. — Gthr. 1893. 
69. Tilapia horii. — Gthr. 1893. 
70. Tilapia rubropunctata. — 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 4J times in length of head 
and equals interorbital width ; mouth large, J 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 J length of 
head and § longest soft rays. Pectoral obtusely pointed, § 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 
finely denticulate, 32-33 ^ ^ ; lat. 1. ^ . Olive-brown above, pale yellow 
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 
