168 A. H. REGINALD BULLEH. 



quite hyaline. The radial patli of the spernuitozoou is so 

 striking that the authors believed it necessary to postulate 

 some attraction^ of the egg for the spermatozoon from a 

 distance. Concerning the nature of the forces, however, no 

 suggestion was made. 



In my own investigations special attention was paid to the 

 direction of penetration of the spermatozoa through the gela- 

 tinous coat of the eggs of Echinus. In this case, at least, 

 it cannot be stated that penetration is always in a radial 

 direction. A great many spermatozoa penetrate obliquely. 

 It appeared to me, however, after having made a large 

 number of observations for determining the point, that on 

 the whole there is a tendency for the spermatozoa to make 

 their way from the outside to the inside of the gelatinous 

 coat. This tendency is best seen after the eggs have been 

 from three to six hours in sea-water and the jelly has become 

 considerably swollen. One then observes, upon adding 

 spermatozoa, that on the whole, although many penetrate 

 obliquely, the spermatozoa pass in a radial manner through 

 the jelly to the agg- It is easy to observe spermatozoa which 

 take an almost perfectly radial course. The path of many of 

 them is seen to incline to a radius by an angle equal to 

 between 10° and 30°. Others may be observed to start 

 fairly radially, soon turn aside, and continue obliquely 

 striking the eggs thus obliquely, or occasionally even making 

 their way out again in a taugeutial direction. A considerable 

 number of spermatozoa, after entering, stick fast in the jelly. 

 The heads of these are then seen to be very variously oriented 

 with respect to a radius. 



Having come to the conclusion that the spermatozoa do 

 pass more or less radially through the gelatinous coat, my 

 next incjuiry was concerniug the cause. It was found that 

 the radial penetration could be equally well observed in (1) 

 a ripe egg ; (2) a full-sized egg which had not undergone 

 maturation, the nucleus being still very large and uncon- 

 tracted ; and in (o) a ripe egg which had been killed with 

 ' Kupd'cr and Bcuecke, loc. cit., ligs. 1, 7, aud 8. 



