230 



V. G. THORPE ON THE LORIGA IN THE GENUS BRACHIONUS. 



stages of this construction. In a Brachionus (Fig. 5) found in 

 Colombo the dorsal plate was distinctly ^^rolonged, but only to 

 the very slightest extent, whilst the basal plate was well 

 defined, evidently the first stage in the production of a distinct 

 species. Such a prolongation of the dorsal plate, concurrently 

 with the existence of a basal plate, would obviously be impos- 

 sible, unless each were separately developed. 



I venture to send this note on the subject in the hope that by 

 discussion, and more especially by a careful examination of 

 varieties, a solution to a puzzling problem may be attained. 

 In addition to sketches, 1 beg also to forward a rough paper 

 model of the lorica of a Brachionus found in China, Australia, 

 and Ceylon as a typical specimen. 



V. G. Thorpe, det 



Explanation op Plate. 



D. Dorsal plate. B. Basal plate. Y. Ventral plate. 



Fig. 1. — Dorsal surface of Brachionus ruhens, showing the 

 division into dorsal and basal plates. 

 , 2. — Side view of Brachionus militaris. 



