NEMATODA REPRODUCTION 



135 



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becomes conical, whilst the protoplasmic portion of the spermato 

 Boon throws out pseudopodia and 

 becomes amoeboid, but ultimately 

 rounds itself oft* again. The sper- 

 matozoa do not attain maturity 

 until they reach the uterus of the 

 female. 



The internal female reproductive 

 organs are, with few exceptions 

 {Trichina, etc.), double, but the 

 yagina. which is lined with cuticle 

 continuous with that covering the 

 body, is always single. They are 

 usually much coiled, and may be 

 divided into ovary, oviduct, and 

 uterus. The ova arise from a 

 polynucleated mass of protoplasm 

 or syncytium (Fig. 65, 0) at the d 

 upper end, and acquire distinct- 

 ness as they approach the oviduct. 

 Fertilisation takes place in the 

 uterus, but the segmentation may 

 not begin until some time after 

 the eggs are laid: in Dochmius, 

 however, it is well advanced at 

 this period, and in many genera, 

 e.g. Pseudalius, Trichina, Dracun- 

 culus, etc., the whole development 

 of the larva takes place in the 

 body of the mother. 



Embryology. The eggs of 

 many of the parasitic forms re- 

 quire a considerable degree of 

 warmth to develop. Those of 

 Ascaris lumbricoides require a 

 temperature of 20 C, those of 

 Trichocephah/s 2 2 '5 C, and those 

 of Oxyuris vermicularis, 40 C. 

 The latter develop in a few hours, 

 the eggs of Dochmius in a few days, whilst those 



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of A. lurnbri- 



