586 E. RAY LANKESTER. 



its surface, which he terms " blasts " (fig. 60). The " blasts " 

 or filiform youug infect a new host when injected into his or 

 her blood by the Anopheles which harbours them. 



I desire to point out that the fission process by which the 

 fertilised zygote gives rise to these filiform blasts resembles 

 the production of microgametes or spermatozoa, and that the 

 blasts themselves are morphologically identical with micro- 

 gametes, whilst a blastophore of residual material accom- 

 panies their evolution. On the other hand, it is a rule in 

 other organisms that the fission products of fertilised egg- 

 cells resemble in form and development the macrogametes or 

 female cells, and do not assume the characters of micro- 

 gametes. The malaria parasite is, it seems, remarkable in 

 being an exception to this rule. The fission products of the 

 fertilised cell are not large cells produced by binary fission, 

 and comparable in size and form to the female cells or 

 macrogametes, but are in form and mode of development 

 identical with male cells or microgametes. We may call 

 them andromorphous or spermatomorphous " blasts " or cells, 

 whereas in other Coccidia, as well as in Volvocinean flagel- 

 lates and in the tissue-foruiing Enterozoa, the " blasts " 

 produced by the fission of the fertilised egg-cell are oomor- 

 phous or gynascomorphous cells. 



In all other cases the spermatomorphous cell seems only to 

 be produced with the special and limited function of zygosis ; 

 it is distinctively a fertilising cell. But in the Hsemamoebidae 

 a generation of spermatomorphous cells is produced which 

 simply carry on their individual life, penetrate the blood- 

 corpuscles of a vertebrate host, and divide into sporocytes. 



We are certainly accustomed to associate the phenomenon 

 of non-sexual reproduction in higher animals with the produc- 

 tion of oomorphous cells. It is only an egg-cell which is 

 capable of multiplication and the production of new indi- 

 viduals of the species, without conjugation with a 

 fertilising cell (parthenogenesis). There are no cases on 

 record, at any rate among animals, of parthenogenesis by 

 means of male cells or male individuals. Speculation and 



