COECILIIDAE 



91 



running water, and there lays about two dozen eggs. The egg- 

 strings become ghied together, entangled into a bunch, and the 

 female coils herself round the bunch and remains in that posi- 

 tion, probably to protect the eggs against other burrowing 

 creatures, as blind snakes {Typlilo}-)S and Mhinophis) and certain 

 limbless lizards, with which the ground literally swarms. During 

 this kind of incubation the eggs assume a round shape, and grow 

 to twice their original size, and the mature embryo weighs four 

 times as much as the newly laid egg. 



The external gills are delicately fringed and red, and they 

 move up and down in the fluid of the egg. The body of the 



W^~^- 



Fig. 15. — /chthi/ophifi ijlullnosa x 1. (After P. and Y. Sarasin.) 1, A nearly ripe embryo, 

 with gills, tail-fin, and still with a considerable amount of yolk ; 2, female guard- 

 ing her eggs, coiled uj) in a hole underground ; 3, a bunch of newly laid eggs ; 

 4, a single egg, enlarged, schematised to show the twisted albununous strings or 

 chalazae within the outer mcmlirane, which surrounds the white of the egg. 



embryo is at first wliite, but becomes pigmented with dark grey. 

 A strong line of lateral sense-organs is formed, and a ring of them 

 lies around the eye and others on other parts of the head. The 

 short tail develops a fin. Of the three pairs of gills the third is 

 the shortest, and is generally turned dorsalwards. In embryos 

 of 4 cm. in length the longest gill measures as much as 2 cm. 

 Yolk is still present in embryos which have reached the 

 surprising length of 7 cm. Then the gills begin to shrink a 

 little, and at this time one pair of gill-clefts breaks through at 

 the base of the third external gill. 



When the larvae are hatched the gills are lost. The young 

 larva takes to the water in a gill-less state, and moves about 

 like an eel. At the bottom of the gill-hole on each side two 

 arches are visible, and there are at this sta^gii-neither inner nor 



