48 DR D. WATERSTON AND DR A. CAMPBELL GEDDES ON EMBRYO PENGUINS 



from the tip of the beak, and consequently the increase in total length is found to be 

 greatest in the last few days, when the beak elongates rapidly, while the figures 

 obtained for the growth of the head in width show a more gradual and regular increase, 

 comparable to the rate of growth of the trunk. 



3. Growth of the Limbs. 



A. Penguin. fore Limbs. The first appearance of the fore limb had the form 

 of a bud-like projection from the lateral aspect of the trunk (fig. 10). This process at 

 first was somewhat spatulate, and then rather bulbous at its free end (figs. 11 and 13). 

 This shape was in turn soon lost, and the limb rudiment assumed the characteristic 

 sickle-shaped form found in the adult bird (figs. 15 and 17, 19 and 23). The two 

 segments of the arm were soon clearly to be recognised and were separately measured. 



The measurements taken were those of the anterior border of the upper segment, 

 together with the anterior border of the forearm from the elbow to the tip. At 1 2 days 

 the total length was 4 mm., made up of I'l mm. of upper segment and 2 '9 mm. of the 

 lower. 



At 19 days the length was 13'9 mm. and at 27 days 297 mm. The rate of growth, 

 therefore, had been such that the length of the limb was more than trebled in the first 

 period, and was more than doubled in the second. Both segments shared the growth, 

 and did so in fairly equal proportions throughout. 



Lower Limb. The portion of the lower limb which was free from the coverings of 

 the trunk was measured in one or in two pieces, as the size permitted. At 12 days 

 it measured 5'4 mm., at 19 days 18'1 mm., and at 27 days 36'2 mm. In the first 

 period the length was more than trebled, and in the second it was again doubled, 

 showing a rate of growth almost exactly similar to that found in the upper limb. 



B. Duck. In the duck corresponding measurements showed that at 12 days (fig. 20) 

 the fore limb measured 15'3 mm. and was nearly four times as long as in the penguin. 

 At 19 days the length was almost doubled (28 "5 mm.), and at the end of incubation it 

 had only added one-third to its length (37'5 mm.). The lower limb, measured in a 

 similar way at 12 days, was 22 mm. in length, again four times as long as in the 

 penguin, and in the specimen of 20 days it was more than doubled, and at the end of 

 incubation it was almost doubled again. 



If the proportion which the length of the limbs bears to the total length of the 

 body be examined, it is found that in the penguin the fore limb at 12 days is almost 

 one-fourth of the body length, that it increases rapidly for a few days until it measures 

 nearly one-half of the length of the body, and maintains approximately this ratio till 

 near the end of the incubation period, when it progresses rapidly and assumes a ratio 

 of rather more than two-thirds of the body length. 



In the duck the ratio at 22 days was one-half, and this proportion became rather 

 larger, but eventually again became nearly one-half. 



(ROY. BOC. EDIN. TRANS., VOL. XLVII., 234.) 



