654 WILLIAM PATTEN. 



nearest the rupture begin to decay, but also five or six, or 

 even more^ which lie at varying distances from the rupture, 

 show more or less decay and parasitic growth in proportion as 

 they are near to or far from the break in the gelatine. It is 

 not difficult to find molluscs' eggs (Limnaeus) where a similar 

 rupture has occurred, and the subsequent growth of fungi has 

 taken place. 



In the case of OEcanthus, which deposits its eggs in holes 

 bored in the small branches of various shrubs, if the eggs are 

 removed artificially and kept in a damp place they become 

 quickly covered with such a thick growth of fungi as to prevent 

 further development by shutting ofi" the necessary supply of 

 oxygen. 



II. Preparation of the Eggs. 



Heat alone was found to be the simplest and best means of 

 hardening the eggs and larvse, which are placed alive in cold 

 water that is very gradually raised to about 60° R. ; the proper 

 time to stop the rise in temperature is when they become hard 

 and white. They are allowed to stand till cool, and then 

 removed to 20 per cent, alcohol, which is increased by 10 per 

 cent, once or twice a day until it has reached the required 

 strength, or about 96 per cent. This method has been used 

 with the best success for insect larvae whose flexible, but 

 impervious, chitinous skins will not allow reagents to penetrate 

 when used in the ordinary way. The great advantage of this 

 method is that it coagulates the tissues without contracting 

 them ; the expansion of the air contained in the body prevents 

 the shrivelling of the larva which results when it is treated 

 with cold reagents. 



The eggs and larvEe were also heated in Kleinenberg's picro- 

 sulphuric acid solution, one third the normal strength, but 

 with far less satisfactory results. 



Since writing the above I have preserved a considerable 

 number of insects' eggs. When picro-sulphuric acid was used 

 and made to penetrate the chorion by means of heat, it was 



