I gO W. L. TOWER. 



2. Alimentary Canal. Entire cuticula lining of both fore and 

 hind gut, including all cuticular structures in the mouth and the 

 linings of the ducts of all the bucal glands. 



3. Trachcal System. All tracheal lining of the main tubes 

 and the smaller trachea, but not of the tracheoles. It is possible 

 that the lining of these latter is not chitinous, or is very soft and 

 does not harden and therefore does not need to be removed. 



4. Internal Supporting Stntctnrts. - -Tentorium, apodemes and 

 the lining of all ducts and glands, including the reproductive 

 organs or such as exist. 



Conclusion. The observations and figures which I have given 

 show that ecdysis is a more important and far-reaching process 

 in the development of insects than might at first be supposed. 

 Inadequate as are the observations herein recorded, they show 

 changes comparable to other periodic phenomena in animals, in 

 the existence of the periods of preparation, active ecdysis, recon- 

 struction, and quiescence. We cannot of course conclude from 

 this that ecdysis is in any way related to other periodic phenomena 

 in animals, but rather that there exists in all a similarity, due in 

 all probability to the existence of deep-seated laws of growth 

 which control all of these phenomena. 



All Arthropods and especially insects cannot grow or further 

 develop without the process of ecdysis, owing to the hard resistant 

 non-extensible chitinous outer portion of the integument. Among 

 insects ecdysis bears a direct relation as far as the specialization 

 of the process is concerned, to the degree of specialization of any 

 particular groups. Thus, in the lower forms like the Campodea, 

 according to Grassi, there is a single ecdysis, but this is fragmen- 

 tary. The integument is shed in small pieces, while in the Col- 

 embola the chitin is shed in bits throughout life. " A species of 

 Peripatus found in the rain forests of Vera Cruz, Mexico, when 

 about one fourth of an inch long did not shed its cuticula at all 

 during its growth. From these primitive conditions of ecdysis 

 found in the most generalized of tracheates and resembling pos- 

 sibly in this function their supposed annelid ancestors, there exist 

 all degrees of specialization up to the most highly developed con- 

 dition found in Coleoptera and Lepidoptera. 



The specialization of ecdysis which goes hand in hand with 



