860 PROCEEDINGS OF THE AMERICAN ACADEMY. 



In the larval histories already published we have endeavored, where 

 they have been observed with sufficient completeness, to discriminate 

 between the congenital and the acquired characters. 



1. Larval State. — A. In this state we have the inheritance of 

 congenital characteristics. 



B. Inheritance of what were originally acquired characters, the 

 results of attacks of enemies. Examples are the tubercles armed with 

 spines aud sometimes with a singular kind of easily detached spines 

 which are hence called caltrops (Empretia, etc.), stripes, spots: all ap- 

 parently inherited at different periods of larval life; the least impor- 

 tant specific and varietal characters probably having been originally 

 acquired during the life of an individual. 



2. Pupal State. — A. Cocoon : the absence or presence of a cocoon 

 was doubtless originally due to differing external conditions : while 

 the dense, perfect cocoon is characteristic of the spinning moths (At- 

 tacidce, Lasiocampidce, etc.) ; the Ceratocampidaa make none at all, 

 but, like the Sphinges, the larvre simply bury themselves in the earth 

 before pupation. In the ArctiidaB and the Liparidoe the cocoon is 

 chiefly composed of the barbed larval hairs, with a little silk to fasten 

 them more firmly together: ir. the Geometridre certain larvae spin a 

 loose thin web. In such cases the spinning of a cocoon is intimately 

 associated with a change of larval habits, and is with little doubt an 

 acquired habit, originally formed by a single individual. 



B. The shape of the pupa is often dependent on the presence 

 or absence of a cocoon. In the NotodontidaB the cremaster is often 

 absent in genera (Gluphisia, which spins a very slight cocoon, and 

 Lophodonta which spins no cocoon) which do not spin a cocoon, 



oval shape of the murre's eggs seem due to the unprotected manner in which 

 they are left on rocks and shelves from which they are liable to fall. Here 

 might be cited the suggestive essay of Prof. John Ryder, " The Mechanical 

 Genesis of theForm of the Fowl's Fgg," (Amer. Phil. Soc. Philadelphia, 1893, 

 XXXI. 203-209,) in which he attempts to show that " the configuration of the 

 outline of the hen's egg is determined by mechanical means, while the egg mem- 

 branes and shell are in process of formation within the oviduct." We may con- 

 trast with the murre's egg that of the robin, in which the shell is thin and uniform 

 in color, since it is protected from harm by being contained in a nest; so also 

 the color of murres' eggs may be due to the action of protective mimicry, the 

 spots assimilating them to lichen-grown or variously tinted rocks, by which they 

 escape the observation of their natural enemies, the fox, the mink, and other 

 egg-devouring animals. So the eggs of Chrysopa, of lice, of many bugs, etc., 

 are in shape and mode of attachment beautifully adapted to prevent them from 

 being seen by egg-destroying animals. 



