CHAPTER V 



SEX AND REPRODUCTION 



Some sexual features. Cries. Scent and scent-glands. Milky and other 

 secretions. Significance of brilliant colouring. Habits in breeding season. 

 Reproduction and care of eggs and young. Maternal extinct in pythons. Vipers 

 swallowing young. Fertility of snakes. Incubation. 



INFORMATION is still deficient with regard to the be- 

 haviour of the two sexes of reptiles during the breeding 

 season, although a few observations have been recorded 

 which show apparently that in the case of some species at any 

 rate much excitement, frequently accompanied by pugnacity, is 

 displayed at this period. A few kinds develop specially brilliant 

 colours, or an intensification of the normal colouring ; but since 

 many reptiles, or, at all events, many snakes and lizards, are at 

 all times more or less brilliantly coloured, and likewise show 

 variations in the brightness of their hues according to whether 

 they have recently changed their skins or not, it is difficult to 

 decide to what extent any or all of the brilliant tints displayed 

 by certain species during the breeding season are due to what is 

 commonly called sexual selection. 



In a large number of instances male and female reptiles are 

 very similar to one another in general characters ; but in other 

 cases there are marked secondary sexual differences between 

 the two sexes. For example, many male lizards are more 

 brightly coloured than the females, and often show special 

 patches of colour which are wanting in the latter. Again, in 

 the family of the Iguanidcs there is often a greater development 

 of the characteristic dorsal crests and gular pouches, or " dew- 

 laps," in the males. For example, the male basilisk (Basiliscus 

 americanus) alone possesses the tall sail-like crest running down 

 the back and tail ; and it is only the male of the horned iguana 

 (Metopocevos cornutus) which carries the three horn-like scales 

 on the forehead characteristic of the genus and species. 



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