DEVELOPMENT OF THE SKELETON OF THE TUATAEA. 9 



in the above-mentioned letter to ' Nature.' Firstly as to the rupture of the egg-shell, 

 to the symmetrical "clean cleft" character of which we drew attention. The 

 following is a drawing of the shell of one of the eggs therein referred to which ran 

 the full time ; and in correspondence with Prof. Dendy concerning it and our 

 suggestion that it seemed to indicate that the shell-breaker may be an actual cutting- 

 instrument, he has authorized us to state his own view, since formed, on opening an 

 egg at Stage S, nearly ready to hatch. He observed that the moment a small 

 puncture is made in the shell, that " splits of itself, very suddenly and with almost 

 explosive violence, reminding one of the bursting of a seed-vessel ; " and he remarks 

 that it has been suggested to him that the splitting may have been assisted by 



Fig. 1. 



Ruptured egg-shell of Sphenodon after the escape of the enclosed young. 

 Full time. Nat. size. 



absorption of moisture from without, by the allantoic fluid 1 . He reverts to the analogy 

 of the well-known " Prince Rupert's drops," and concludes that " the function of the 

 very sharp shell-breaker is probably to make the small incision ;" and that when that 

 is done, the egg, being in a condition of high tension, simply bursts open. And he is 

 the more inclined to this view from having noted that the shell of an egg contained 

 in sand which had been " somewhat excessively moistened " prematurely burst, and 

 revealed within its interior a dead embryo in an insufficiently advanced stage of 

 development. 



In the afore-mentioned letter to 'Nature 'we recorded certain details concerning 

 the treatment up to the time of hatching of the eggs brought us by Mrs. Dendy. The 

 three young Sphenodons which from these we successfully hatched out were kept in 

 confinement in the incubator (Hearson's, size A I.), at the temperature at which they 

 were hatched viz. 25 Centigr. They were fed upon mealworms, small earthworms, 

 cockroaches, and flies, as best obtainable. For these the individual taste was 

 observed to vary somewhat. One little creature exhibited a decided preference for 

 mealworms, and a " tug-of-war " for the possession of an earthworm or cockroach was 

 a not unfrequent occurrence. 



1 Cf. also Dendy, 99 c . p. 251, 



VOL. xvi. PART i. No. 2. February, 190]. c 



