THE UNPAIRED ECTODERMAL STRUCTURES OF 

 THE ANTENNATA. 



MINNIE MARIE ENTEMAN. 



A STUDY Of the Strepsiptera, and an attempt to relate their 

 peeuliar reproductive system to that of other insects, f^rst 

 suggested the homologies which it is the object o this paper 

 to establish. The material was furnished by I rot. U. VI. 

 Wheeler, of the University of Chicago, to whom I am also 

 indebted for much kindly help and valuable suggestion. 



The unpaired median ectodermal structures of insects are of 

 two kinds : ( I ) ehitinous apodemes, or frucae, which occur m the 

 thorax and serve for the attachment of muscles ; (2) chitm-lmed 

 tubes or sacs, belonging to the various segments of the abdomen 

 and forming the terminal, more or less differentiated portion of 

 the o-enital duets. A study of the occurrence of these struc 

 tures%hroughout the Antennata. together with their embryonic 

 development in a few forms, seems to indicate that they are 

 homologous and derived from a series of segmental invaginations 

 which were originally developed in relation to the appendages 



Considering first the apodemes : they are of very general 

 occurrence throughout the insects, -we might even say the 

 A thropoda,-yet so far as I know little attention as been 

 .iven to their structure and method of development^ They 

 :sually consist of rod- or T-shaped inward P™)-;'°-/™^;^'>; 

 interseo-mental portion of the chitmous integument. Some- 

 Zll These projections are solid, but oftener they are hollow 

 hToughout their external third or fourth, thus S-ing evidenc 

 of the'ir invaginate origin. The various parts may be bent 

 curved and give rise to minor projections, and their appear 

 Tnce may be further complicated by the union of successiv 

 ap demel The free ends give attachment to muscles, and 

 r i^itermediate part supports the connectives of the nerve 

 chain. 



