558 LIFE : OUTLINES OF GENERAL BIOLOGY 



it in repair by adjusting the weed and by blowing in more bubbles. 

 If a water-snail intrudes, who would devour the developing eggs, 

 he drives it away; if an egg falls out he picks it up and blows it back 

 into shelter. When the helpless fry are hatched out, he continues to 

 look after them. How altruistic the whole behaviour of the male 

 bubble-nest fish, but why is he so keen that the mother shall have 

 none of the credit? We ask this, and the beautiful bubble bursts, 

 for in aquaria at least, when the young ones begin to move about 

 actively, the lately "altruistic" father is the first to make them his 

 prey. 



In mankind we know of matriarchal and patriarchal families — 

 or at least matrilinear and patrilinear — and of the modem type 

 where the two parents count more equally; but there is a fourth kind 

 of family, which only animals could illustrate. It is explained by 

 Alverdes in his recent book on animal sociology, to which we are 

 much indebted. It is the children family, and it is said to be illus- 

 trated at various levels, e.g. by reindeer, certain kinds of whales, 

 some of the pythons, certain fishes like herring, and some caterpillars 

 like those that form processions. But these combinations of young- 

 sters of the same age may be ranked as incipient societies rather 

 than as families. 



Monogamous Animals. — Many fishes multiply in a very auto- 

 matic way, without almost any relations between the sexes. The 

 personal touch is practically a-wanting; for the eggs are shed from 

 the ripe ovaries or roe, the sperms making the milt are similarly 

 shed by the males, and fertilisation takes place fortuitously in the 

 water. In most cases all that can be said is that the presence or the 

 spawning of the one sex serves as a stimulus to the other. Very 

 gradually, however, in a minority of cases the personal touch has 

 evolved. That is to say, it is possible to make a series from the mere 

 contact of males and females up to elaborate courtship. Two pipe- 

 fishes may twine their bodies together; in sharks and skates there 

 is internal fertilisation ; and from such simple beginnings of personal 

 relations there is an inclined plane leading to the elaborate ongoings 

 of sticklebacks and bubble-nest fishes. In one of the South American 

 cat-fishes there is a prolonged courtship, then an embrace, and then 

 a hiding of the fertilised eggs in a safe corner. 



There is an interesting little fish called the Bitterling that lays 

 its eggs in the gill-plate of the freshwater mussel. It is a gregarious 

 fish; but at the breeding season the individuals separate in pairs, 

 coming together again when the sex-urge is past and hunger is 

 once more the ruling passion. This is what might be called seasonal 

 monogamy. Thus two scarabee beetles live as mates for the season 

 and help one another to make and roll the balls of dung which 

 serve as stores of food both for themselves and for their offspring. 



