94 Phylum Protozoa 



from 14 to 19 graduated chambers, from 3 to 12 hours are required for 

 the addition of each new chamber. Under optimum conditions _ an 

 individual will mature usually in from 19 to 23 days, and at that time 

 produce from 30 to 40 young by multiple fission. In the larger species 

 of Elphidium, in which the test consists of from 40 to 50 chambers, it is 

 doubful whether more than two generations occur annually. Since the 

 life span determines the frequency with which one might expect to 

 encounter individuals in a state of reproductive activity, it will be less 

 difficult to obtain cytological evidence in support of a proposed life cycle 

 in small quickly maturing species, and a more abundant supply of ma- 

 terial will become available in a given time. 



The following method of collecting and maintaining these organisms 

 in culture has proven satisfactory for species of Discorbis, Pyrgo, Trilo- 

 culina, Bulimina, Patellina, Spirillina, and Robulus, and should be satis- 

 factory for small species found within the limits of the intertidal zone. 



An abundant supply of living Foraminifera may usually be obtained 

 by washing seaweed or eel grass vigorously between the hands and allow- 

 ing the organisms, sand grains, and other bits of debris to settle through 

 a piece of bolting cloth into the bottom of a glass vessel. A convenient 

 glass bucket for this purpose is made from a 10- x 14-inch battery jar 

 provided with a rope handle and covered with canvas for protection. 

 The bucket should be equipped with a tubular net 8 inches deep 

 attached to a wooden hoop that will rest on the upper rim of the bucket. 

 The vertical sides of the net should be made of unbleached muslin and 

 the flat bottom of No. 00 bolting cloth. 



After allowing the organisms about one minute to settle, the water 

 should be decanted. Repeated washing by decantation^ will free the 

 collection from silt and a considerable amount of organic debris that 

 would decompose later. If several collections are to be made the material 

 must be transferred to another container. A set of glass refrigerating 

 dishes 6 inches in diameter and 2 inches deep that stack one on top of 

 the other is convenient for this purpose. A carrying rack should be 

 provided for the dishes and, where the collecting ground is some distance 

 from the laboratory, it is advisable to control the temperature by packing 

 with ice. 



The rate of mortality is high in newly collected material, and we have 

 found at La Jolla that certain species that will survive at room tempera- 

 ture for more than a year do not reproduce until the temperature is 

 lowered to 18 C. or less. Therefore, it is well to sort the material after 

 the Foraminifera have become acclimatized to laboratory conditions. 



Crowding of newly collected material should be avoided at all times. 

 Not more than 5 cc. of the washings containing the Foraminifera should 

 be placed in each of a number of 4-inch round-bottomed finger bowls 



