98 



EVERS'S COMPARATIVE ANATOMY. 



reproduction appertain to animals unprovided with special organs 

 of generation. 



In oviparous generation, which belongs to birds, many reptiles 

 and fishes, the egg^ after fecundation, passes through the oviduct 

 from the body of the parent, to be hatched by the influence of 

 external agents. Most mammalia afford examples of the viviparous 

 form of generation, here the ovum remains within the uterus of 

 of the female until it is capable of independent life. Many animals, 

 however, besides mammalia, bear their young alive, examples of 

 which are to be met with among the reptiles, fishes, mulluscous 

 and articulate animals. The last form of generation above alluded 

 to is the ovo-viviparous, which implies the production of living 

 foetus, the ovum being hatched within the body of the parent; 

 but never contracting a vascular connection with the uterus, this is 

 the case with the monotremata, as the echidna, and ornithorhynchus, 

 and also with the monotrematous marsupiata, as the opossum, and 

 kangaroo. 



All the higher classes of animals possess generative organs of 

 two kinds, the co-operation of which, for the purposes of reproduc- 

 tion, constitutes the distinction of sex, into male and female. 



The following table exhibits a view of the reproductive process 

 in the different classes of animals, as given by Dr. Thomson, of 

 Edinburgh, in his matchless article on generation, in the "Cyclo- 

 paedia of Anatomy and Physiology." 



f Parent splits, each part a new ani- 

 mal. 

 J 1. Transverse, 

 f Fissiparous . . \ 2. Longitudinal. 

 3. Irregular. 

 I Parent splits and discharges the 



Non-sexual 



o 



O 



J-H 



youn< 



v Sexual 



I r«o™™^o™„„ $ Budding upon the parent stock. 

 ^Gemmiparous . J Separat b ed Du ds, gemmae, or sporules 



1. On all parts of the body. 



2. On one part or organ only. 



f Hermaphrodite Both sexual organs on one individual. 



1. Self-impregnation. 



2. Mutual impregnation. 

 'Oviparous laying eggs which are 



hatched. 

 1. External fecundation. 

 L Dioecious . . <{ 2. Internal fecundation. 



Ovo-viviparous, eggs hatched within 



the maternal body. 

 .Mammiferous, suckling the young. 



1. Monotrematous. 



2. Marsupial. 



3. Placental or strictly viviparous. 



Prom the above table, it appears that there are a vast number of 

 animals wholly destitute of generative apparatus, and where organs 

 first appear, the animals seem to have the power of pro*J5agati ng by 

 means of ova, without copulation ; in many of the lower animals, 



