Affective Tendencies 379 
at first simply endured by one of the parents, either 
father or mother, finally become actual “needs” to this 
parent. 
It is likewise true of the relations of external incuba- 
tion (brooding) which arise at first as the result of some 
particular circumstance and in this way become a habit. 
For instance the attachment manifested by the female 
spider Chiracanthium carnifex for her nest, whether it 
be her own or one of which she has taken possession, 
grows with time, that is with the length of her occu- 
pation of it. Hence “mother love” seems in her case 
to be really nothing but her attachment to a home to 
which she has become accustomed.?° 
It is just the same with the brooding of birds and 
some reptiles, which owes its origin to the pleasant sen- 
sation which the contact with the fresh eggs brings in 
the feverish condition accompanying the egg-laying 
process, but which by habit has become in itself an in- 
stinctive inclination.*? 
Finally as regards lactation the young have gradually 
developed secretions in the lactiferous glands by sucking 
the secretions of the perspiratory glands on the breast of 
the mother brooding over them, and thus they have at 
the same time so accustomed the mother to this process 
that lactation finally becomes an actual need for her. 
“With mammals we must look for the origin of the 
mutually symbiotic relations which unite mother and 
child in the phenomenon of lactation. The physiological 
disorders of pregnancy and parturition lead, among other 
very curious trophic effects, to an excessive secretion of 
20A. Lécaillon, “Sur la biologie et la psychologie d’une araignée,” 
Année psychologique, Année toe, pp. 63-83. Paris, Nasson, 1904 
21Giard, op. cit., p. 266, 
