222 Dr. C. Shearer. On the Oxidation Processes of 



consumption for 1 minute = 015 c.mm. The same eggs fertilised consumed 

 in the first minute after the addition of the sperm 12 c.mm. of oxygen. 

 Thus, the addition of the sperm to the eggs causes, within the space of 

 1 minute, an increase in their oxygen consumption of something like 

 80 times that observed on the same eggs 1 minute previous to the addition 

 of the sperm. 



The examination of sections of fixed material of the eggs of & micro- 

 tuberculatus during different stages of the process of fertilisation shows that 

 the sperm take at least 10 to 15 minutes to enter the cytoplasm of the 

 egg. In material fixed within 2 minutes of the sperm being added to the 

 eggs, the sperm are seen onfy attached to the external surface of the egg 

 membrane. They have not penetrated the membrane itself. 



This initial oxygen consumption of the egg immediately on fertilisation 

 must be brought about by the first contact of the sperm with the external 

 surface of the egg membrane. We arrive then at the remarkable conclusion 

 that contact of the spermatozoon with the external surface of the egg is 

 capable of increasing its oxygen consumption in 1 minute by something 

 more than 8,000 per cent. In fact, the total oxygen consumption of the 

 eggs shown in figs. 1 and 2, represents some change brought about in the 

 egg by the spermatozoon before it has entered the egg, and before it has 

 formed a male pronucleus in the egg cytoplasm. It is moreover clear, that 

 when the fusion of the male and female pronucleus takes place at a later 

 stage of the process, it is not accompanied by any fresh rise in the oxygen 

 consumption of the ovum, but instead, a slight drop in the curve is often 

 observed about this time (see fig. 3). The nuclear features of syngamy 

 therefore, seem connected in no direct way with the oxidations taking 

 place in the ovum during fertilisation. 



In fig. 3 is shown a graph of an experiment which illustrates these 

 points. It represents the amount of oxygen taken up and the carbon 

 dioxide given off during the fertilisation of a quantity of eggs that con- 

 tained 2 - 8 mgrm. of egg nitrogen. The curve extends over a period of 

 1 hour after the sperm were added to the eggs, and so to a time when the 

 first segmentation division has been completed and the egg has attained the 

 two-cell stage. The readings are in 2-minute intervals up to the end of 

 10 minutes, and after this at 5-minute intervals. At the end of 2 minutes 

 10 - 5 c.mm. of oxygen had been consumed, which compares favourably for this 

 quantity of eggs, with the figures obtained in the previous experiments, the 

 graphs of which are shown in figs. 1 and 2. 



It will be seen that at the end of 15 minutes the curve begins to 

 appreciably flatten, and this flattening increases at the 25th minute when 



