TREMATODE. 387 



5.— NOTE ON A TREMATODE WITH CILIATED 

 INTEGUMENT. 



By WILLIAM A. HASWELL, D.Sc, Professor of Biology, 

 University Sydney. 



The presence of a coating of cilia is always laid down as 

 one of the principal points which characterise the Turbellaria 

 as distinguished from the class of worms most nearly related 

 to them — viz., the Trematodes. In this respect the larvae of 

 certain of the Monogenetic forms of the latter class — 

 Epibdella, Udonella, Diplozoon, Potystomum — help to bridge 

 over the gap between the two groups ; but in all of these the 

 cilia are lost not long after the larva leaves the eg^, and long 

 before the sexually-mature condition is attained. 



Certain of the species of Temnocephala, however, — a genus 

 which in other respects occupies a quite isolated position 

 among the Trematodes, aiford us exceptions to this rule. 

 Cilia are present on the surface of T. minor and T. dendyi 

 (both of which frequent the surface of the common small 

 Crayfish, Astacopsis bicarinatus of Australia) in the full- 

 grown and sexually-mature condition. In the former species 

 they extend over the greater part of the body, the tentacles 

 and the sucker, however, remaining free from them. They 

 are most numerous and most active immediately behind the 

 bases of the tentacles ; further back they become more 

 scattered and are less constantly in action. In T. dendyi 

 they are confined to a limited space behind the bases of the 

 tentacles. Where they are present these vibratile cilia stand 

 in marked contrast to a series of non-vibratile sensory cilia 

 (the cilia of the " tactile cones ") which occur along with 

 them, being curved, highly flexible, and whip-hke. 



I do not consider that this discovery need alter to any 

 great extent our views of the affinities of Temnocephala. 

 Braun^ lays great stress on the presumed absence of cilia in 

 Temnocephala as separating that genus from the Rhabdocoele 

 Turbellaria, with which he considers it to be in many ways 

 allied ; but, as he recognises, the integument of the Temno- 

 cephalecB is quite different from that of the Rhabdoccela in 

 other respects, save in the supposed absence of cilia ; and in 

 other parts of its organisation there is, as I hope to show in a 

 detailed paper shortly to be published, not much real affinity 

 between the two groups. 



Brown's " Klassen und Ordnungen des Thierreichs," Vermes, p. 521, 



