52 



HELLER 



adult; they remain very similar in shape, in all the species, for a 

 considerable time. All the young observed possessed striated shells 

 but adults seem to retain or lose this character indifferently in most of 

 the species. 



Growth takes place by additions to the outer border of each plate 

 along the soft white seams and probably continues as long as life 

 exists ; the largest specimens possess the whitish seams which mark 

 the growing edges of the plates. In youth the annual increase is 

 probably much greater than later. A specimen from Iguana Cove, 

 weighing 29 pounds when taken, doubled its original weight in twelve 

 months accompanied by an increase to the margin of each plate of the 

 carapace of about half an inch or an inch to the diameter of the plate. 

 Its total gain during the year was in length of carapace four inches, in 

 breadth three inches, and in height, one and one-fourth inches. During 

 the colder winter months the consumption of food was greatly lessened 

 and growth correspondingly retarded. The increase in weight during 

 the summer months amounted to nearly three pounds monthly. This 

 tortoise now weighs 130 pounds, having gained 100 pounds in three 

 years. This rapid increase may be abnormal but it shows how rapid 

 their growth may be under favorable conditions of food and warmth, 

 which we believe are even more favorable in the Galapagos where no 

 cool winter season retards their growth. 



The extermination of the gigantic land tortoises in the Galapagos 

 seems to have been due chiefly to inroads made upon them by the 

 whalers, orchilla pickers and the " oilers." The tortoises were abun- 

 dant in the early part of the nineteenth century and the whaling fleets 

 frequenting these waters captured great numbers of them for food. It 

 was the practice of these vessels to take several hundred away alive to 

 be used as desired. In this way many hundreds were taken from the 

 islands. What the whalers began the orchilla pickers and "oilers" 

 completed. The orchilla pickers who visited the archipelago annually 

 for several years to gather orchilla {Roccella) used the tortoises for 

 food wherever they could be obtained. In their search for orchilla 

 they visited the higher altitudes where the orchilla is most abundant 

 and incidentally captured such tortoises as were safe from the whalers 

 by nature of their habitat. These people brought with them their 

 domestic animals, dogs, cats, pigs, etc., which upon their departure 

 were left on the islands to complete or rather continue the extermina- 

 tion. Of these animals dogs and pigs have been most destructive in 

 digging up the eggs and eating the young. The " oilers " have been 

 perhaps the most destructive agents. It was the business of these 



