40 U. S. BUREAU OF FISHERIES 
ducted jointly by Dr. Prytherch and Dr. R. R. Kudo, show that part 
of the development of this micro-organism takes place in the intestine 
of the mud crabs, Panopeus herbsti and Hurypanopeus depressus, and 
part in the gills, muscle, mantle, and other tissues of the oyster. The 
mud crabs, which are abundant on oyster beds, feed on the infected 
tissues of dead oysters from which millions of spores of the parasite 
may be obtained. The developmental stages of the parasite in both of 
its hosts have been followed and the complete hfe history outlined. 
The sporozoan is apparently a new species of the genus Porospora 
and is similar to the form Porospora portunidarum found on the 
French coast which has an alternation of hosts between crabs of the 
genus Portunus and the mollusk Cardiwm edule. 
Observations on the oyster borer, Thais—FPrevious investigations 
have shown the destructiveness of the conch or borer, Z’hais floridana, 
to oysters; hence some means of control was sought by R. O. Smith at 
Apalachicola, Fla. The Louisiana method of trapping spawners on 
stakes appeared feasible; therefore on April 18, 1936, 75 stakes were 
planted on a selected part of a bar in St. Vincent Sound where large 
numbers of conchs were present. This method is based on the tendency 
of spawning females to climb before depositing egg capsules. Green 
gumwood poles, 2 to 3 inches in diameter and 12 feet long, were 
wrapped with fresh palmetto leaves from the bottom to the water line 
and firmly planted along the oyster bar in depths varying from 4 to 7 
feet at low tide. It was found that the palmetto leaves served no 
purpose other than to expedite removal of conchs and egg capsules 
and the leaf wrappings were discontinued. 
Capsules were first taken on May 25, the last previous examination 
having been made May 15. Bottom temperature on the bar on May 
26 was 24.2° C. The stakes were increased to 120 and were lifted 
every other day, weather permitting. The average daily take of 
capsules was 100 in June, 200 in July, and 1,340 during the second 
week of August, after which spawning ended abruptly. In all, 20,000 
capsules were removed from the stakes and destroyed. Observa- 
tions on the correlation between salinity and deposition of capsules 
showed that a drop in salinity is regularly accompanied by reduc- 
tion in number of capsules deposited. 
In the laboratory 50 adult Zhais were kept in a large tank for 
experiments and six were placed separately in battery jars, running! 
sea water being supplied to all. The average number of eggs 
laid.in a season by a full grown female of 8.0 cm (31% inches) total 
length is approximately 200. The average number of eggs per 
capsule, as observed in capsules from five different females, was 
approximately 4,000 each. Total egg production per female per 
season is therefore around 800,000. 
What is believed to be a chemotropism was discovered in sexually’ 
mature females. If capsules are placed in a jar with a mature fe- 
male she will deposit her capsules next to them. If she lays more 
than once the second group is placed near the first, and in the mass 
experiment, only rarely were capsules scattered about the tank. The 
bulk of the spawning by all females was done in close proximity to 
other capsules and this was observed throughout the summer both, 
in the field and in the laboratory. It has long been believed that the 
heavy deposition of capsules in one area is the result of a group mi- 
