PROGRESS IN BIOLOGICAL INQUIRIES, 1935 427 



where the salinity ranged from 19.05 to 24.25 and were absent in 

 salinities lower than 15 parts per mille. A total of 1,527 drills were 

 collected, TO percent of which were alive, the others having been 

 killed by the freshets of the previons winter. Eighty-three percent 

 of the total were Vroscdpinx cinerea: and 17 percent, Eupleura 

 caudata. 



In South Carolina, in cooperation with the State Board of Fish- 

 eries, a general survey of oyster pests in the coastal region from the 

 Santee River to the Savannah River was conducted for the Bureau 

 by G. Robert Lunz, Jr., of the Charleston, S. C, Museum. Samples 

 of oysters collected at 132 representative stations show that the 

 boring sponge and drill are the principal enemies of economic im- 

 portance in this section. Over 41 percent of all oysters collected 

 were infested with the boring sponge, particularly the more com- 

 mon species, Cliona ceJafa^ which at many stations showed prolific 

 growth and honeycombed the shell of from 80 to 100 percent of the 

 oysters. Serious shell injury by this pest is limited almost entirely 

 to beds lying below^ low tide level in the more saline areas near the 

 inlets, where oysters on both natural and planted beds rarely survive 

 for more than 2 j^ears because of sponge attack. 



Damage by drills is limited for the most part to spat and small 

 seed oysters occurring chiefly in a zone extending from 1 foot above 

 low water mark to the bottom of the bed. Other pests found oc- 

 casionally are the starfish, conch, and borer, none of wdiich were 

 found to be causing serious damage during the present survey, In 

 several localities a heavy growth of common anthozoan coral, Gor- 

 gonia^ w^as found on beds below" low tide level where it apparently 

 causes indirect injury and smothering of oysters by reducing the 

 circulation of water and increasing the deposition of mud and sand. 



During the period from September 15 to November 15 a general 

 survey of the oyster pests on the Georgia coast was conducted in 

 cooperation with the State department of game and fish. Observa- 

 tions made at 141 stations extending from the Savannah River to 

 the St. Mary's River, sho^v an abundance of drills on the natural 

 beds, and an extensive and severe infestation of oysters by the boring 

 sponge. Studies of drill distribution in relation to salinity show 

 their presence at salinities from 10.4 to 30.6, the maximum abundance 

 occurring in salinities from 24.3 to 27.7, or an average of 18 drills 

 per sample. The boring clam, Martesia^ was found to be a pest in 

 this region, infesting the shells of 24 percent of the specimens exam- 

 ined, but in no case "was it so abundant as to cause serious weakening 

 or injury to the shell. Specimens of the borer, Ptirpura^ and the 

 conch, Busycon^ were collected at 27 stations in salinities ranging 

 from 17.6 to 30.4, but were not sufficiently numerous or destructive 

 to oysters as greatly to reduce their production in this region. 



Studies of the parasitic microorganism found in oysters in Louisi- 

 ana, Virginia, and North Carolina were continued at the Beaufort 

 laboratory by Dr. H. F. Prytherch. An improved technique was 

 developed wliereby rapid examination of the fresh tissues of spat 

 and adult oysters coulcl be made to determine the degree of infection 

 by this protozoan, and the various stages in its life history. Exam- 

 inations of over 750 spat collected during the period from March to 

 December, show that the heaviest infection of the oyster tissues oc- 



