406 ON THE BREEDING-HABITS OF A CICHLID FISH. [Apr. 28, 



Bolti ; but a complete account of the nesting-processes has never 

 been published. 



On visiting the fish-markets on the shores of the lake, and 

 inspecting the baskets full of Boltis, the first thing to strike one 

 is the fact that some individuals are more brilliantly coloured than 

 others : these the natives declared to be males, the females being 

 less vividly coloui'ed. I accordingly dissected and sexed a few- 

 examples, and found this statement to be correct. 



The males, which grow to a larger size than the females, have 

 the whole of the ventral surface of the head and belly, almost as 

 far back as the commencement of the anal fin, of a bright red 

 colour ; the throat is of a particularly brilliant hue. The pectoral 

 and pelvic fins are bright red, and the top of the head also bears 

 red pigment — not, however, so vivid as on the ventral side, and 

 inclining rather to violet. 



In the females, on the other hand, the red colour is absent from 

 the top of the head and from the pectoral fins ; the throat and 

 belly are pink. 



The brighter colours and the large size of the males render 

 these easily distinguishable from the females, even when viewed 

 in the water. 



In common with many other Cichlid fishes, I'ilapia nilotica 

 excavates holes for breeding-purposes ; these were first observed 

 by Loat in Lake Menzaleh. In Lake Qurun these nests or, 

 as the natives call them, "houses" of the Bolti are to be found 

 close to the shore in two to three feet of water. I found them 

 to occur almost exclusively on the north or desert side of the 

 lake. The reason for this is, I think, quite evident to anyone 

 familiar with the Birket el Qurun ; for on this side the water 

 becomes rapidly deeper offshore, enabling the fish when disturbed 

 to dart off into deep water, where they are safe from their 

 numerous enemies. On the south side of the lake the conditions 

 are very diflferent, there being often fifty yards of muddy shallows 

 to cut ofi" their retreat. 



The nests are merely basin-shaped holes scooped out in the 

 sand, usually among reeds or tamarisk bushes. The largest one 

 I saw measured just over a yard in diameter and one and a half 

 feet deep. I had the good fortune to be able to watch a Bolti at 

 work on one of these nests. The latter was nearly completed 

 when I commenced my observations at the beginning of May 

 and was occupied by a large male with brilliantly coloured head 

 and fins ; there were no signs of a female in the neighbourhood. 

 The male remained by himself in the nest during the two days 

 that I observed him, and was occupied chiefly in smoothing down 

 the sides of the excavation ; this he did by revolving round and 

 round with his tail in the centre, brushing aw^ay dirt from the 

 sides of the ne&t with his fins. On the third day I returned 

 early to the nest and found it unoccupied. A short distance 

 away, however, the same male was to be seen now accompanied by 

 a female ; courtship was evidently in progress, the male swimming 



