264 Shaw.— The Fertilization of Onoclea. 
half the diameter of the latter. In following the development 
of Osmunda 1 he found that the spermatozoid loses its 
pyramidally coiled form after it comes in contact with the 
egg-nucleus and before the two fuse. In his work with 
Marattia 2 he found the spirally coiled spermatozoid in 
contact with the egg-nucleus. In a later stage he found two 
nuclei present which seemed to be the male and female 
nuclei. They were not very different in size or appearance. 
He concluded that the female nucleus had become smaller, 
and that the spermatozoid had changed into a similar nucleus. 
‘ The two nuclei,’ he writes, ‘ then gradually fuse, but all the 
different stages could not be traced. Before the first division 
takes place, however, but one nucleus can be seen, and this 
nucleus resembles the nucleus of the unfertilized egg.’ From 
these accounts it has been concluded that the spermatozoid 
of the Ferns enters the egg in the condition in which it swims 
free, and then, on coming near to or in contact with the 
egg-nucleus, it undergoes a change in structure which makes 
it more like the latter and also like the resting nucleus in the 
sperm-cell of the antheridium. In this respect the details of 
fertilization are much alike in many plants, and the behaviour 
of the animal spermatozoon is strikingly similar. This is 
shown by Van Beneden’s account of fertilization of Ascaris 3 , 
in which the spermatozoon, after entering the egg, rapidly 
changes and forms a typical nucleus exactly similar to the 
egg-nucleus. 
Preliminary Investigation. 
The differences in size, structure, and habits between the 
male and the female gametes are greatest in those plants in 
which the condition of the gametes during fertilization has 
been least studied : viz. the Archegoniatae and the Characeae. 
In the fall of 1895 the writer made some microtome-sections 
1 Campbell ’92, p. 70 ; ’95, p. 348. 2 Id. ’94, p. 9 ; ’95, p. 261. 
3 Wilson ’96, p. 133 (refers to Van Beneden 1883-87-88). 
