G. GENERAL NATURAL HISTORY AND ZOOLOGY. 329 



as tlie ray-like bodies so long preserved in the museums of 

 Copenhagen, Kiel, Christiania, and Trondhjera. 3. The exist- 

 ence of this sieve-like apparatus indicates, Avith certainty, 

 that the mode of life of this shark resembles that of the 

 whalebone cetaceans ; and that, so far from its being a fish 

 which is dangerous from its carnivorous propensities, it lives 

 on small animals, caught in masses by means of this sieve. 

 4. The presence of these rays and their teeth-like structure 

 furnish quite peculiar generic characters to Selache. 5. The 

 form and nature of these branchial rays show that the genus 

 Selache existed in the seas of Europe at least in the tertiary 

 period, as the Hamiovera aurata of Van Beneden has been 

 found in the Belgian crag. The similarity, in habits, of this 

 hark to the great Rhinodon typicus of the tropics, as de- 

 scribed by Dr. Percival Wright, is alluded to by Steenstrup, 

 who likewise very justly suggests that the food of both fishes 

 is of the same nature. 13 A^ July 15, 1873, 269. 



DETERMINING SEX IN BUTTERFLIES. 



A paper was recently published in the Americaii Natural- 

 ist by Mrs. Mary Treat, in which she attempts to show that 

 whenever lepidopterous larvae are deprived of food, or this 

 is stinted in amount, in the interval between the last two 

 stages, males are produced in most cases ; but when the food 

 is regularly supplied, and in quantity sufticient for the wants 

 of the larvce, the opposite sex is almost invariably produced. 

 These observations are indorsed and supplemented in a pa- 

 per by Mr. Thomas G. Gentry, as published in the proceed- 

 ings of the Academy of Natural Sciences of Philadelphia, his 

 conclusions having been suggested by having confined a num- 

 ber of larvjB of Attacus cecro^na in a box, and neglecting to 

 supply them with food for four days. These larvae had ad- 

 vanced toward their final change, possibly within a week or 

 ten days, when, on opening the box, the greater number were 

 found to be concealed within cocoons ; the remainder wan- 

 dering about, as if seeking some opening by which to escape. 

 These were at once removed to another box and provided 

 with nutriment, upon Avhich they immediately commenced 

 feeding. In a few days they began to assume the chrysalis 

 form ; and after several weeks Mr. Gentry was surprised to 

 find that those which changed first proved without exception 



