52 SPOLIA ZEYLANIOA. 



or perhaps to a CcBtiurufs bladder, and, like these, i?. undoubtedly to 

 bo referred to the six-hooked embryo. The first developmental stage 

 observed by MctschnikoflE appeared to be a solid ball of about 0-OS 

 mm. , with an unusually tliick cuticular envelope and cellular contents. 

 The latter subsequently became clear on attaining a diameter of 0'14 

 mm. , when the embryo lies on the inner surface [of the cuticle] in the 

 form of a cellular layer. Soon the buds begin to form, and that exclu- 

 sively from the cellular wall, which becomes thicker at certain spots 

 and sends little projections into the inner cavity. Although at first 

 flat and connected by their broad bases with the cellular wall, the 

 protuberances, as they grow larger, gradually detach themselves 

 from the subjacent layer." 



Thus although the prohferating Cysticercoid of placuna is not a 

 Polycercus. yet it is an analogous f orm , for which the provisional 

 name Merocercxis may be suggested. Looked at broadly it seems to 

 represent a type intermediate between Monocercus and Polycercus. 

 The latter, according to Haswell and Hill, " is not nearly related to 

 EchinococciLS , but finds its closest ally in Staphylocystis " (out of 

 Glomeris). 



Mortality of Placuna. 



The direct observation of mud-burial in the Sambore river 

 and the collection of many prematurely dead specimens in lake 

 Tamblegam indicate the existence of a destructive agency in the 

 rainfall. 



Mr. H. O. Barnard, Superintendent of the Meteorological Branch, 

 has kindly supplied me with information on this matter (see the 

 Appendix to this report), from which it appears that there was in fact 

 an exceptional downpour of rain at Trincomaloe in January, 1907, 

 the bulk of tlie rain falling wdthin the space of a few days. This 

 is of the nature of a torrential or catastrophic cloud-burst, causing 

 freshets and floods and boding ill to placuna. 



The average rainfall for the month of January at Trincomalee for 

 the last 37 years is 5 • 66 inches ; in January, 1906, the actual rainfall 

 was 2-28 inches; in January, 1907, 10 '23 inches, of which 5 '42 

 inches {i.e., nearlj' the whole average) fell during the first four days 

 of the month. The actual figures are January 1, 0*29 ; January 2, 

 2 • 27 ; January 3, 2 • 00 ; January 4, • 86. The figures for the other 

 months of the rainy season at Trincomalee are given below, the 

 average being reckoned for the last 37 years : — 



Inches. 

 October average . . . . 7 ' 83 



1905 .. .. .. 3-90 



1906 .. .. 8-68 



