THE MALE-CELL OR SPERMATOZOAN 



105 



moment of fertilization arrives. Important perhaps is the observation, .mainly 

 due to Flemming, that the head of the sperm not only arises from the nucleus of 

 the mother-cell, but almost wholly consists of the chromatin-elements of the 

 same. 



Fig. 28. — Spermatozoa of crayfish (a), lobster (/>), crab (c), ascarid {d), 

 water-flea — moina (<•). man {J), ray (g), rat (/*), guinea-pig (1), 

 a beetle — immature stage (A'), sponge (/). 



IV. Physiology of the Spermatozoan. — A few facts in regard 

 to the physiology of the sperm demand notice, (a) It is specialized 

 as a highly active cell ; its minimal size, the usual absence of any 

 encumbering nutritive material, the contractility of the tail, and the 

 general shape, all fit it for characteristic mobility. More than one 

 histologist has likened it to a free muscle-cell, and its resemblance to a 

 flagellate monad has already been noted. (Jf) Furthermore, the sperm 

 has very considerable power of persistent vitality. Not only does it 

 often remain long unexpelled in the male animal, without losing its 

 functions, but it may retain its fertilizing power after remaining for 

 weeks, or even months, in the female organism. In the earthworm, 

 the spermatozoa pass from one worm to another, not directly to the 

 ova nor to female ducts, but to be stored up in special reservoirs or 

 spermathecae. So it is with many animals. The spermatozoa received 

 by the queen-bee during her single impregnation, are for a considerable 

 period — even for three years — used in fertilizing successive sets of 

 worker and queen ova. Quite unique, however, is the case of one of 

 Sir John Lubbock's queen-ants, which laid fertile eggs thirteen years 

 after the last sexual union with a male. The spermatozoa had 

 apparently persisted all that time. Hensen cites the facts that a hen 

 will lay fertilized eggs eighteen days after the removal of the cock ; 

 and that in bats, spermatozoa may remain alive a whole winter in the 

 uterus of the female, (r) Remarkable too, and again like monads, is 



