374 DESIGN IN NATURE 



In the amphibia, of which the frog (Rmm temporaria) is a good example, the conjugation or confluence of the 

 sexes is more intimate. In this case the male frog takes his place on the back of the female, and while she is 

 depositing her spawn he sheds his milt over it. The spawn thus fertilised, aided by heat and moisture, soon 

 develops into tadpoles, which swim about like fishes and are water-breathers. The tadpoles in due course shed 

 their tails and gills or branchiae, and develop four legs and lungs and become air-breathers. The reproduction of 

 the frog is vital in all its stages. It is in no way dependent for its initiation and accomplishment on external condi- 

 tions or environment, although these latter aid in the process. The developing frog gradually but surely produces 

 organs which enable it to leave the water and assume a terrestrial existence : the water does not form the branchiae 

 and swimming tail, neither does the earth form the four legs. All those wonderful transformations, which adapt 

 the animal first for an existence in the water and subsequently for an existence on the land, are spontaneous, vital, 

 and independent. The frog in its various stages of development is superior to its surroundings and environment. 

 All the really important transformations are from within and vital, and are in no sense due to irritability of 

 constitution or external stimulation. 



In the reptiles coitus takes place, the females producing eggs which they either hatch out themselves or bury 

 in the sand to be hatched out by the heat of the sun. 



Similar remarks are to be made of birds. In this case the eggs are hatched out by the mother or artificially 

 by incubators ; the hatching being a mechanical process. The impregnation of the eggs, which is a vital act, takes 

 place at an early stage of their development. The impregnation is in no sense due to irritability and extraneous 

 stimulation. It sufiices if the hving male and female elements are simply mixed as apart from coitus. The forma- 

 tion and transmission of the eggs down the oviduct are representative vital acts, and furnish the most remarkable 

 illustrations of the powers of life and vital movements known. There is no irritability and no extraneous stimula- 

 tion anywhere. The egg is formed by vital processes, and the oviduct transmits it from the ovary to the cloaca 

 by vital acts. The oviduct also supplies the egg, during transmission, with its various membranes and coverings, 

 but (and this is the remarkable feature) the developing egg does not, as is generally believed, act as an irritant, and 

 produce its transmission along the oviduct or its expulsion from the cloaca. 



The oviduct is expressly formed to receive, contain, and transmit the egg by a series of peristaltic movements 

 in all respects resembling those of the oesophagus, stomach, intestine, bladder, uterus, heart, and chest. The peri- 

 staltic movements are inherent and fundamental, and are not dependent on irritability or stimulation of any kind. 

 The bolus does not cause the peristaltic movements of the oesophagus, the food those of the stomach and intestines, 

 the urine those of the bladder, the foetus those of the uterus, the blood those of the heart, the air those of the chest, 

 or the egg those of the oviduct. 



If they did cause the movements in question, the structures referred to could not possibly act as receiving and 

 containing structures. The fact that they are receiving and containing, as well as transmitting and expelling struc- 

 tures, shows plainly enough that the peristaltic or rhythmic movements must begin and terminate in the structures 

 themselves. Structures endowed with peristaltic movements have, as a rule, a fundamental and very important 

 vital function to perform. They are necessary to the continuation of life, and occupy a unique position, in so far 

 that they are not subject to extraneous control, or even the control of the will. 



The peristaltic structures are to be regarded as special creations devised for the express purpose of carrying 

 on life, and the most important details of life, in its several departments. They invest life with a superior dignity, 

 and make it very little dependent on environment and mere externalities. They make living things superior to 

 dead things. The plant and the animal are on a higher platform than their surroundings ; they are living, active 

 factors, and control the inanimate matter which surrounds them. They select and appropriate certain portions of 

 it, and cause it to circulate within their bodies. They reject other portions, and eject at intervals the detritus of that 

 originally selected. 



In mammals the reproductive process is in some respects the most complicated. Indeed it is held by some 

 to represent in its several phases all the other forms of reproduction referred to above ; the developing mammal, 

 according to them, being in succession a fish, an amphibian, and a reptile, or at all events exhibiting peculiari- 

 ties which associate it with the several orders of animals named. Thus it has gills or branchial arches and blood- 

 vessels like a fish and amphibian, and a mixed circulation like a reptile. 



The male and female organs and elements in mammals are situated in different individuals, and conjunction or 

 coitus in the ordinary sense is the rule. In certain abnormal conditions coitus has been dispensed with, the semen of 

 the male being simply injected into the vagina of the female. The essential act of reproduction in the mammal, as 

 in all other cases, consists in the union and interpenetration of the male and female elements. In the human species 

 it is now known that the spermatozoon or male element actually plants or buries itself in the ovum or female element, 

 and that unless this intimate union and commingling takes place neither impregnation nor conception occurs. 



