1893.] Joint Formation Among the Invertebrata. 97 
of joint. Other cases might be mentioned as that of the lower 
jaw and the tarso-tibial joint. 
In the above remarks, I have simply made an attempt to 
apply the theory of mechanical genesis to a much neglected 
group of the invertebrata, and if I, in this, have only been able 
to direct attention to the field of carcinology, I will feel that 
this short paper will have served its purpose. 
