NATURAL HISTORY OF AMERICAN LOBSTER. 31? 
tact with the egg possess an adhesive power; they seem to shorten, and thus to pull the 
sperm cell into position.® 
In this critical situation when the conditions for fertilization are favorable some- 
thing pulls the trigger and fires the gun. That is to say the capsule explodes and shoots 
backward, while the head in consequence of the rebound leaps forward and is driven 
through the chorion and into the egg. 
The space between the inner and the outer capsule is filled with a peculiar explosive 
substance, which according to the ideas of Koltzoff possesses the property of swelling 
up when it meets with water. Water must either enter through pores of the inner tube 
or be absorbed through the outer wall of the capsule. The extension or swelling of the 
explosive material is rapid and is usually attended by an evagination of the inner tube 
and discharge of the central body. 
The sperm cell is thus deformed by the action, and since the character and degree of 
the evagination varies with the physical and chemical conditions present the number 
of these apparent artifacts is very great. 
In actual conditions or in 4.2 per cent isotonic solutions of calcium chloride in sea 
water, it is possible to follow every step of the discharge. Labbe in 1894 described the 
discharge of the capsule as the final developmental stage of the sperm. The explosion 
of the capsule seems to liberate the elastic energy of a coiled spring represented by 
the central body, which may show a spiral form in Pagurus or a series of beads, bands, 
or granules. 
In abnormal capsular explosion, according to Koltzoff, there is a double spring of 
the sperm, first forward and then backward. If the suggestion of the free movements 
of sperm given above, and for which I am alone responsible, should prove to be an error, 
these abnormal explosive movements might account for the contractile pulsations 
described by*Bumpus. 
According to Koltzoff the energy of the explosion is contained in the explosive 
material. When the chitin plug of the inner tube is driven out, water enters and even- 
tually penetrates to the inner capsule and brings on the explosion. My suggestion that 
water might enter the inner tube and be driven out by a contraction of the protoplasmic 
layer surrounding the capsule, thus causing the cell to move forward, presupposes that 
water does not at once penetrate the capsule and reach the explosive substance. If 
this really happens the suggestion regarding locomotion would be untenable. 
No special stimulus was found which would effect a normal capsular explosion, 
and it is possible that the sperms respond to a coordinated series of stimuli. Nothing 
is yet definitely known upon this subject. 
According to Koltzoff the head and neck containing the proximal central body 
are driven into the egg and take part in fertilization, while the capsule, with its 
processes, in whole or in part, and the distal central body, are left outside and disappear. 
Notwithstanding the difficulties, owing to the great size and opacity of the egg and 
the small size of the spermatozoa, Koltzoff observed a single case where a normal sperm 
“ Koltzoff also offers a different and contradictory explanation of the adhesion of the sperm cell to the egg, namely, that the 
egg membrane appears in many cases under the microscope to be finely porous, and that the processes are driven like so many 
splinters into these pores. 
