vni MAY-FLIES 299 



to spring. In the same way the nerves of the body 

 are given off from the ten other ganglia. Paired 

 connectives issue from each ganglion, and unite it to 

 the next, so that the cord appears to be divided along 

 a considerable part of its length. The nerve-cord may 

 be demonstrated in an uninjured larva, by inflating 

 the body with air from behind. By this means the 

 cord is pressed against the integument, and can be 

 seen with a lens, or even with the naked eye. 



" There are two ovaries in the female, resembling 

 the ovaries of Fishes. Each is supplied with in- 

 numerable air-tubes. The eggs are so small that they 

 cannot well be observed without the aid of a lens. 

 They are of a flattened oval form, and of white colour. 

 Their small size in comparison with that of the adult 

 Insect is explained by the fact that the larvae grow for 

 three years before they arrive at maturity. 



" The emergence of the fly takes place in warm and 

 still weather. Shortly before emergence, the wings 

 are observed to become prominent, though still 

 enclosed within the larval skin. The intestine is 

 emptied, and the colour of the animal changes in 

 consequence. 



" When all is ready, the larvae quit their burrows, 

 and swim freely in the water. The time of emergence 

 is usually towards evening, and always in the summer 

 months. In the year 1671, I saw the Palingenia 

 flying about from the I3th of June. 



" When the larvae have left their burrows, they 

 make their way with all speed to the surface, and the 

 transformation is effected with such rapidity that even 

 the most attentive observer can make out little, except 



