PART III 

 BIOGONY 



A. ONTOGENY. Development of the Individual. 



I. ASEXUAL REPRODUCTION. 



Occurs by Fission, Budding, Segmentation, and has been studied 

 in the Protozoa and Protophyta, Hydra, etc. If time permits study 

 in detail prepared slides showing the process of fission in Sten- 

 ostoma. 



II. SEXUAL REPRODUCTION. 



a. Monogony; sexual reproduction with only one parent. 



1. Parthenogenesis (virgin reproduction). Observe and draw 

 water fleas (Daphnia) containing broods of young produced from 

 unfertilized eggs. The same phenomenon may be seen in plant 

 lice (Aphides.) 



2. Paedogenesis (infant reproduction). Observe and draw 

 stages in the development of unfertilized eggs in the larvae (sporo- 

 cysts, rediae) of the tematode worm, Diplodiscus. 



b. Amphigony; sexual reproduction with two parents. 



i. Oogenesis and Spermatogenesis. Study prepared sections of ; 

 (i) Ovotests (hermaphrodite gland) of the snail, Planorbis, and 

 draw a portion of the section to show the ova, the spermatozoa, 

 and the method of development of each. (2) Ovary of the frog, 

 showing eggs of very different sizes. Note the enormous size of 

 the nucleus (germinal vesicle). It is rilled with nuclear sap, in 

 which are scattered nucleoli and fine threads of chromatin. Note 

 the distribution of the yolk and pigment in the egg. Draw. (3) 

 Testis of frog, showing mature spermatozoa, their heads attached 

 in bundles to nurse cells and their tails extending into the lumen 

 of the seminiferous tubule. Around the walls of the tubule are seen 

 the following stages in the formation of spermatozoa : (a) Sperma- 

 togonia, cells with clear nuclei, at periphery, (b) Spermatocytes I, 

 large cells with chromatin in clumps, (c) Spermatocytes II, 

 smaller cells with densely staining nuclei, (e) Spermatozoa, with 

 progressively elongating nucleus and cell body. 



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