350 Effa Fmik Mnhse. 



44, 59, 61, 63, 67). The bulk of the secretion in the himen of the 

 mature glands is, however, densely granular (Fig. 61). Artificial 

 stimulation causes the secretion to flow from the lumen of the small 

 glands, and in small amounts from the outer parts of the mature 

 glands. It appears as a transparent liquid on the surface. If the 

 stimulus is continued, the liquid on the surface becomes milky, due 

 to the expulsion of the densely granular secretion from the mature 

 glands. This mixes with the secretion already on the surface. 

 Further stimulation causes a continuation of the flow and the dis- 

 charged liquid becomes thick and creamy, even yellowish. If this is 

 wiped away, the last liquid to appear from the gland just before 

 exhaustion is again milky. 



The concentrated liquid, bearing the poison granules, is poured 

 out and spreads into the more transparent liquid that has already 

 come to the surface. The granules of the mature secretion are known 

 to have an irritating or poisonous effect on the mucous membranes 

 of other animals. If, therefore, the secretion is poured out when 

 the animal is stimulated or irritated by an enemy, the advantages 

 that must accrue to the toad are apparent. 



Production of secretion in relation to age. The mature glands of 

 the adult toad may differ greatly in the relative time of their ex- 

 istence. The first gland buds that arise in the tadj)ole develop 

 quickly into glands with mature secretion (Fig. 10). As compared 

 to the large glands of the parotids of the adult, these first glands 

 are very incompletely developed. There is, however, a gradual 

 groAvth and it is possible that in many instances the mature glands 

 of the adult are the end results of the first buds to arise in the tad- 

 pole. Such glands may, however, have been called upon to fully 

 discharge at some time, and in that case will have degenerated. 

 Since buds may arise at any time, after their first appearance, during 

 the life of the animal and develop into mature glands, the places 

 of discharged glands are filled in this way. Consequently we see 

 that there may exist in the same region of two individuals of the 

 same age, or even side by side in one individual, mature glands which 

 differ greatly in their relative age. 



I have previously traced the development of a bud that has arisen 



