Femur and Trochanter in Arthropods. 161 



dynamics. Prof. Deluge biomechanics, and W. Roux the 

 mechanics of development (Entwickelungsmechanik) . 



The Arthropods in the case of which we observe, either in 

 all the thoracic limbs or in only a single pair, the fusion of 

 two consecutive joints, which ensures autotomy *, appear 

 among those the growth of which takes place by means of 

 ecdyses, during which these animals often have much diffi- 

 culty in freeing their limbs from the old cuticular envelope, 

 because these members are very long, are terminated by enor- 

 mous pincers (lobster, crabs), or are provided with large 

 foliaceous adornments (leaf-insects) f. It is probable that in 

 these different cases the mechanical actions produced at the 

 moment of ecdysis must have contributed in a large measure 

 to the development of the peculiar structure in question. I 

 shall shortly publish a detailed study on the Arthropods in 

 which this is found. 



In the Phasmids the phenomena of autotomy must have 

 already begun to appear before the complete fusion of the 

 femur and trochanter, the articulation corresponding to these 

 two joints then constituting a locus minoris resistentue. At 

 the outset many of these insects must have perished from the 

 results of hemorrhage. Then, a perfecting process gradually 

 setting in and being transmitted by heredity, the number of 

 the survivors increased. The regenerative faculty must at 

 first have been but slightly marked, and the first regenera- 

 tions must have been very imperfect. Then, as the fusion 

 between femur and trochanter tended to take place more and 

 more, there was more regularity in the sections corresponding 

 to the amputations, and, in consequence, more regularity in 

 the portion reproduced, until the moment when regeneration 

 was capable of furnishing a limb with a tetramerous tarsus, 

 the joints of which were sharply differentiated one from 

 another. 



I therefore believe that this peculiar condition is to be 

 regarded as an example of a character acquired by use, by 

 functional excitation, and then transmitted by heredity, as 

 fast as it advanced towards perfection. 



My experiments upon the regenerations following artificial 

 amputations lead me to suppose that an altogether special 



* This does not imply that all the Arthropods in which autotomy is 

 found to occur must necessarily exhibit fusion between two consecutive 

 joints of their limbs. 



t I have recently been able to remark phenomena of autotomy in leaf- 

 insects which had been sent to me from the Seychelles. In these Ortho- 

 ptera the fusion between femur and trochanter exists. 



