INTRODUCTION. 



Ixxvii 



Fig. xl. 



some cases I have met with ovicells developed over the 



upper extremity of the aviculariau 



beak and mandible, clearly indicating 



their morphological relation to the 



orifice of the zocecium. On more than 



one occasion this liisus has occurred 



to me in Schlzoiheca fissa (Woodcut, 



fig. xl.)*. 



(ii.) The resemblances in minute 

 detail between the avicularian cell and 

 the ordinary zocecium of the species 

 to which it belongs, which are not 

 unfrequently met with, have a like 

 significance. Thus, to take a single 

 illustration, in one species a minute 

 sinus occurs on the lower margin of the 

 avicularian mouth, corresponding with 

 a similar sinus in the orifice of the 

 zocecium. instances of the same kind might be multiplied. 



The function of the avicularia is difiicult to determine ; 

 nor, indeed, can the same function be assigned to all of 

 them. The primary forms are many of them quite unfit 

 for prehensile work. The lid-like mandible, with plain 

 rounded margin, has no power of grasping, and could not 

 detain for a second the active worms which are some- 

 times captured by the articulated kinds. Their service 

 for the colony must lie in some other direction. Even 

 the fixed, transitional forms, in which the beak and curved 

 mandible are present, must be inefficient for this work 

 from their want of mobility, whilst in many of them the 

 parts concerned in the act of prehension are but slightly 



* Another case is recorded on p. 240. 



Avicularian eel 

 ov. OTicell. 



