Introduction to Animal Morphology. 35 



or carried by ducts, called respectively oviducts and 

 vasadeferentia. All reproductive processes seem only 

 to differ from growth processes in that the results are 

 discontinuous, and they may be divided into two 

 series ist. Agamogenesis, where no second or male 

 element is required to stimulate the (often internally 

 produced) germ into development. The simplest form 

 of agamogenesis, leaving out of account fission and 

 gemmation in plastides, is the production of the so- 

 called winter eggs in sponges, where we have a con- 

 stant and, as far as we know, continuous asexual pro- 

 pagation not necessarily interrupted by any periodic 

 recurrence of sexual reproduction. Such a form is 

 monogenetic agamogenesis, as the progeny and parents 

 are similar. In another case a primary form or proto- 

 zooid produces, by internal gemmation (without having 

 any developed sexual organs), a secondary form or 

 deuterozooid, and this may in time produce a tritozooid, 

 or it may develop sexual organs and produce ova, 

 which require the male elements to fertilize them. To 

 this process the name metagenesis has been given, and 

 of it there are varieties : thus, when the deuterozooid is 



:ial, and so differs from the protozooid, the process 

 is metagenesis with successive lictcro^ouy, or if the pro- 

 tozooid be sexual, and by internal gemmation give 

 to a deuterozooid in which sex organs are also 



doped, the metagenesis is said to be re//// contempo- 

 raneous ]iclerogon\\ and it may 1><> is,<^enetic or diverse^ 

 according as the deuterozooid agrees or disarm -s with 

 tli<- jiroio/ooid i \Vln-n- ihi-r' are successions 



only of t\V" , the Dai sometimes 



:i in ]>la<:<' of m is. 



In other casus tin- protOZOOids havr 



