384 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1925 



Mic 



ever, is not a simple filament ; under a high-power microscope there 

 can be distinguished in it a number of parts: First, there is a head 

 (fig. 7. I), E, J, a) containing the nucleus (Nu), then comes a short 

 body or middle piece (b), and finally a long, tapering tail (c). The 

 tail acquires the po^Yer of movement and can be lashed sideways 

 with a wavy motion, which lashing drives the sperm forward with 

 much speed when the sperm is innnersed in a liquid. The male 

 germ cell has now become virtually a minute one-celled animal, and 

 has arrived at the stage in which it is capable of fertilizing a ma- 

 turated egg cell. 



All the processes thus far described concerning synapsis and ma- 

 turation of the germ cells, antl the transformation of the si)ermatids 

 into .spermatozoa aj)i)ly to animals in general, including man, and it 



must not be supposed they are limited to 

 insects. The processes have been exten- 

 sively studied in insects becau.se they are 

 more easih^ seen in many in.sect germ 

 cells than in the cells of higher animals. 

 The same is true of fertilization, a de- 

 scription of which will soon follow, but 

 many of the accessory })rocesses as the}' 

 occur in insects are peculiar to insects. 

 During uniting, for example, the sper- 

 matoz(ja from the male insect are stored 

 in a special .sac within the body of the 

 female. This sac, known as the sper- 

 matiieca. is connected with the outlet 

 duct of tlie female's ovai'ies. Tiie eggs may not be deposited for 

 some time after mating, tiie time varying with different species, 

 sometimes a few hours, sometimes a few days, or a considerable 

 length of time may elapse. With the honeybee the spermatozoa are 

 capable of remaining alive and functional in the queen for three or 

 four years. 



Whenever an egg is laid a number of spermatozoa in a spermatic 

 rupiid are discharged from the sperm sac upon the upper end of 

 the egg as the latter goes by the mouth of the sperm sac. Some of 

 lhe.se spernuitozoa almost invariably find their way into the egg 

 through a minute aperture in the shell, the micropyle (fig. 2, Mic), 

 penetrating the vitelline membrane and entering the egg plasm by 

 the force of their own motion (fig, 8). The first of these sperma- 

 tozoa to reach the egg nucleus is the one that mates with it; the un- 

 successful i)ci-ish in the egg and are probably abs()i'])ed in the yolk. 



k;. S. — Diagram rcpresautiiig the 

 eutranee of spermatozoa il^pin) 

 into the ess tlnougli tlu' mic- 

 ropyle (1/Jc). ChOj cliorioii ; \'u, 

 egg nucleus after niatuiation ; 

 I'J{, polar bodies 



