58 CEYLON PEARL OYSTER REPORT. 



temperature was 78*1 F., and at 7 P.M., on the south central part of the Cheval 

 Paar, the temperature was 79'5 F. At both times the specific gravity was 1"023. 



A bottom tow-net which had been down all night was found on the morning of 

 February 26th to contain great quantities of small Copepoda with very long caudal 

 setaa (Ectinosoma roseum and E. atlanticum), also Euterpe acutifrons and a dozen 

 other species, along with some Medusoids and Ctenophores. 



About mid-day, when going under easy steam, we put out a tow-net which we had 

 contrived with a canvas funnel in front of the mouth and having the narrow end 

 forwards, so as to reduce the volume of water entering and so the pressure on the 

 net. It worked well and gave us good hauls containing chiefly Nauplei, Zoeae, 41 

 species of Copepoda, including the large blue PontelJa securifer and the small long- 

 tailed Ectinosoma atlanticum, Centropagcs violaceus, Metacalanus auriviUii (common), 

 Pseudodiaptomus auriviUii (male previously unknown), and also Ceratium (two 

 species), Peridinium, some Trochospheres, Radiolaria, many Diatoms, especially 

 Coscinodiscus and long rod-like forms, Sagitta, Salpa, Appendicularians, Pteropods, 

 and some Lamellibranch fry. It was evident from this and many other hauls that 

 the microscopic plankton of the sea, both at surface and bottom, was very abundant 

 in the Gulf of Manaar, and this must be of very great importance in feeding the pearl 

 oysters. 



We boarded the barque " Rangasameepoiawee " later in the morning, and found 

 that she was anchored on the position of the " shoal-buoy," a mark that Captain 

 Donnan has been in the habit of bringing with him on each inspection in order to 

 indicate the north end of the long shoal which runs northwards from Karativo 

 Island to the southern part of the Cheval Paar. The buoy (a large structure of 

 casks and planks bearing a mast) is anchored over a sunken tank, and serves as a 

 useful mark to take bearings from during the inspection of the banks. 



"We now set the divers to work to bring us up samples of the bottom, a rather 

 coarse white quartz sand upon which great masses of fine green and red filamentous 

 Algas grow. These contained Hypnea musciformis, and undetermined species of the 

 genera Cladophora, Ceraraium, and Cluetomorpha. 



The divers brought up quantities of this weed, upon which, when put in our small 

 glass aquaria, we soon found great numbers of very young pearl oysters the spat 

 being densely crowded in some places on the filaments of Algas. The smallest size, 

 of which there were very many, was about - 5 millim. in diameter, but other samples 

 measured up to 4 millims. This spat was evidently very young and the smallest 

 had probably just become attached during the last few days. A quantity was kept 

 alive under observation, some in wooden tanks on the barque and some in our glass 

 aquaria on the "Lady Havelock." It was found to be restless and active, and to 

 leave its attachment and crawl freely about on the Algas or on the glass sides of the 

 aquaria. For example, one specimen (a) crawled 5 inches up the glass within 

 18 minutes, the last 2f inches in 12 minutes: another (h) crawled '> inches in 



