OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 231 



Notes upon and Comparison of the Measurements. 

 The measurements were analysed along several different lines. 



1. General Growth of the Trunk. 



A. Penguin. — The vertex to coccyx length of the specimen of 12 days (fig. 10), taken 

 as it lay in the egg, i.e. in a flexed position, was 15 "5 mm., while that of the duck of 

 corresponding age was practically twice as great, namely, 30*6 mm. In the penguin 

 the rate of growth from this date onwards was fairly uniform and progressive, and the 

 largest embryo, that of 30 days, measured 61*2 mm. in the same position. The 

 specimen labelled as being 24 days was larger than those of 25 and 26 days, and 

 among the other specimens similar anomalies were present. Taking the maximum 

 measurements of specimens which seemed to be typical in their rate of growth, we 

 found that the length attained at 12 days was doubled at 19 days and doubled again at 

 27 days, the progression being thus almost in geometric ratio. 



The same ratio is found to exist when measurements of the breadth of the specimen 

 are taken. The maximum breadth attained at 12 days was rather more than doubled 

 at 19 days, and rather less than doubled again at 27 days. 



B. Duck, — The maximum length of the embryos of this species was uniformly 

 greater than that of the penguin of same age. Even the largest fully developed 

 penguin embryo was smaller than the largest duck embryo. At 12 days (fig. 20) the 

 duck embryo was almost exactly twice as long as that of the penguin of corresponding 

 age. The rate of growth from this date onwards, as ascertained by the same criteria 

 as in the case of the penguin, was, however, much slower than in that creature. 



At 19 clays the length had increased only by rather less than one-half, i.e., was 

 4'36 cms. as against 3"06 cms., and not until the 23rd day of incubation was the length 

 doubled, and from this time until the end of incubation the increase again was rather 

 more than half, from 43*6 mm. to 76'8 mm. The breadth figures showed a rate of 

 growth very similar to that found in the penguin. The breadth at 12 days was 10 mm., 

 and this figure was practically doubled at the 19th day and almost doubled again at 

 the end of incubation. 



2. Rate of Growth of Different Segments of the Trunk. 



Penguin. — Analysing the rate of growth of the different segments which make up 

 the vertex to tail measurement, the head segment is found to increase slowly at first, 

 but grows rapidly in the last few days, while the neck increases rapidly through all 

 stages. 



The growth of the trunk and tail follows the general rate of the whole body, the 

 length attained at 12 days being doubled at 19 days, and doubled again at 27-28 days. 



The figures for the head are modified by the fact that measurements were taken 



TRANS. ROY. SOC. EDIN., VOL. XLVII. PART II. (NO. 10). 34 



