BT R. J. TILLYARD. 



^7 



beyond noting the changes in the external form of the gill during 

 the groM'th of the larva. Before a satisfactory solution of the 

 phylogenetic problem can be attempted, the ontogeny of the 

 internal structures of the gill must be fully understood. These 

 gaps in our knowledge it will be my chief endeavour to fill in 

 the course of this paper. 



Material Studied. 



For the purposes of this paper, a very large amount of material 

 has been gathered together, from many widely separated locali- 

 ties. In this connection, I desire to record my deep appreciation 

 of the valuable help afforded me by Mr. F. W. Carpenter, M.A., 

 Science Master at Sydney Grammar School. He has accom- 

 panied me on many of my collecting expeditions, and it has only 

 been through his zeal and energy that many of the rarest and 

 most valuable larval forms have been obtained. In particular, I 

 desire to thank him for the discovery of a fine series of larvae of 

 Diphlebia lest aides from Went worth Falls, N.S.W., and many 

 larvH? of Xeosticta cmiescens from Heathcote, N.S.W. Both 

 these larva? are rock-dwellers, and can only be obtained by wading 

 into very cold water, and lifting out a large number of heavy 

 rocks. Mr. Carpenter has also wielded the dredge-net for me 

 with great success, and most of the specimens taken in this 

 manner at N^ational Park must be credited to his energy. To 

 my brothei-j the late Lieut. S. J. Tillyard, 5th Royal Berks., I 

 am indebted for a fine series of fixed larvae of Diphlehid euphoi- 

 aides, from rocky streams at Kuranda and Yungaburra, N. 

 Queensland, as well as for my only two specimens of the rare 

 larva of Nosasticta salida. My thanks are also due to Professor 

 P. P. Calvert, of Philadelphia, U.S.A., for larvai of Calapteryx 

 and Heta'7'hia, to Mr. G. Howes, of Duuedin, N.Z., for larvae of 

 Aihstrolesfes r.aleitsav is and Xauthaoieiuis ze/audica, and to Mr. J. 

 Bridwell, of Honolulu, Hawaii, for a number of larvae of Ayrian 

 astelice, a very peculiar form with reduced caudal gills. 



I append herewith a tabular list of all the forms studied. The 

 names given under the type of gill-system are those used in this 

 paper, and will be found defined in their respective sections. 



