NATURAL HISTORY OF AMERICAN LOBSTER. 317 



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. 



