EECTAL BREATHING-APPAEATUS IN ANISOPTEEID DRAGONFLY LARV^. 127 



A Study of the Rectal Breathing-Apparatus in the Larvse of Anisopterid 

 Dragonflies. By R. J. Tillyard, M.A. (Cautab.), B.Sc. (Sydney), 

 F.lIs., F.E.S. 



(Plates 18-22, and 21 Text-figures.) 



[Read 4th May, 1916.] 



Page 



Iiitroductiou 127 



Historical Summary 128 



Terminology 131 



Methods 134 



Material Studied ■ 138 



General Study of the Branchial Basket 139 



Study of Gill-types : — • 



A. Simplex System ". 143 



1. Undulate Type 145 



2. Fapillate Type 147 



B. Duplex System 150 



1. Implicate Type 151 



2. Foliate Type 153 



3. Lamellate Type 160 



The Basal Pads 170 



The Tlypobranchial Tissue 177 



Ontogem^ of the Gills in ySschna and A^iax 179 



Phylogenetic Conclusions 188 



Bibliography 192 



Explanation of the Plates 194 



Postscript 195 



Introduction. 



The present paper is the outcome o£ a suggestion made to me some three 

 years ago by my friend Dr. F. Ris, of Rheinau, Switzerland. Being unable 

 to spare the time to carry out the researches which lie had begun, and of 

 which he later on published a short account (23), he very kindly suggested 

 that I should take up the subject, which promised to yield many interesting 

 facts new to science. Through his generosity in giving me full information 

 as to his methods^ and in sending me a set of prints of his very beautiful but 

 unpublished microphotographs, I was able to apply his methods to the rich 

 Australian material at my disposal. The immediate result of this was the 

 discovery of a number of new and interesting forms of rectal breathing- 

 apparatus. Later, I undertook the study of the finer details and histology of 

 these organs by means of microtome-sections. This method again yielded a 

 number of new facts not less in interest than the former, although the great 



