THE ARTHROPOD SPERMATOZOON

SUMMARY Machilis distincta Janetsch spermatozoon has been studied by both the transmission and scanning electron microscopes. This spermatozoon, otherwise normal in the sequence of its various portions, is endowed with some peculiarities, the most striking of these being its bending on itself head-to-tail at maturity. Owing to the fact that both halves are invested by a common membrane, the wrong impression is gained that the functional unit consists of a pair of spermatozoa. The accessory fibres, compressed by two conspicuous lateral structures are confined to either side of the flagellum. When the spermatozoa reach the spermatheca the accessory fibres are seen to be packed together by a material which is glycoprotein in nature. In the mature sperm both the acrosome and nucleus appear helically coiled and encircled by a sleeve of microtubules.