AMERICAN ZOOLOGISTS AND EVOLUTION. 15 



discovered the moth which fertilizes the flower, but finds an anoma- 

 lous change in the maxillary palpi of the insect, by means of wbich 

 the moth collects bundles of pollen, which it inserts into the stigmatic 

 tube, and during this peculiar act deposits her eggs in the young fruit. 

 Prof. Riley has reasons to believe that this is the only insect engaged 

 in the fertilization of this plant. A mutual dependence is here met 

 with of extreme interest. The yucca unfertilized forms no fruit, and 

 the larva of the moth consequently perishes. 



Prof. Augustus K, Grote, in an examination of butterflies, finds 

 successive gradation in their structures, and shows that as these or- 

 gans " become less serviceable to the insect they become more rigid 

 and in position more elevated above the head in the butterfly, while 

 in the moth they are more whip-like and directed forward." While 

 protesting against the separations which have been made in the order 

 based upon the antenna?, he directs attention " to the real differences 

 in antennal structure between the butterflies and moths, while show- 

 ing that the antenna? are modified by desuetude in the higher and 

 former group." Prof. Grote, 1 in dealing with a family of moths, the 

 Noctuidce, calls attention to the unequal value of Acronycta, and is 

 forced to admit that these differences become clear through the 

 theory of evolution. He says : " Where in Acronycta there is a gen- 

 eral prevailing uniformity in the appearance in a single group of spe- 

 cies and generally broad distinctions between the larval forms, it is a 

 not unreasonable conclusion that these larval differences are gradu- 

 ally evolved by a natural protective law, which intensifies their char- 

 acters in the direction in which they are serviceable to the continu- 

 ance of the species." 



Those who have believed in types as fixed laws, rigidly impressed 

 at the outset of life, are those also who have recognized in the cells 

 of a honey-bee, as well as in the arrangement of leaves about the 

 axis of a plant, a perfect mathematical adjustment of parts, which 

 were stamped at the beginning, and have so continued to exist with- 

 out deviation. For nearly two hundred years it has been believed 

 that the instinct of a bee guided it to shape a cell which of all other 

 forms should use the least amount of material. A theory having been 

 established as to the constant shape of a bee's cell, namely, that it 

 was an hexagonal prism with trihedral bases, each face of the base 

 being a rhomb with certain definite angles, a mathematician w T as 

 given the problem to construct similar cells, and to determine the 

 best possible form with the use of the least amount of material. The 

 coincidence between theory and observation and experiment was so 

 remarkable as to settle apparently for all time the question as to the 

 perfectly-implanted instinct of the bee with its unconscious power of 

 accurate work. Prof. Jeffries Wyman, 2 to whose memoir I am indebted 



1 " Proceedings of the Buffalo Society of Natural Science," vol. i., p. 130. 



2 " Proceedings of the American Academy," vol. vii., p. 68. 



