462 



SCIENCE 



[N. S. Vol. XLII. No. 1083 



vacuoles the offspring of any individual may 

 Bave immediately following division. Some of 

 the possibilities observed up to date are illus- 

 trated below. 



(a) (A) (c) (d) (e) (/) (g) (/:) 



23333445 

 2 22 23 23 "' "' "' " 



34 24 23 34 



Apparently at division two vacuoles are 

 added in the normal way as a rule (one to the 

 posterior end and one to the anterior). This 

 is not invariable as is evidenced by (b), {d) and 

 (Ji). As stated above, although a Paramcecium 

 of this race may not show an increase of 

 vacuole number up to the time of division it 

 has not lost the power to produce extra 

 vacuoles. In cultures started with two- 

 vacuoled forms, individuals have been found 

 showing three and four vacuoles. The most 

 common distribution at division in the three- 

 vacuoled individuals is three vacuoles to the 

 posterior part and two to the anterior half. 

 There is no fixed order in the distribution of 

 the vacuoles at division and no definite time 

 at which the extra contractile vacuoles appear 

 in the life cycle of the individual. The only 

 definite statement that may be made of this 

 race is that it has a tendency to more than two 

 contractile vacuoles. 



The race is strong and healthy and some of 

 the individuals are very large. There is no 

 invariable relation between the size of the ani- 

 mal and the number of vacuoles. A small ani- 

 mal may have more than a larger one. Since 

 the race has been under observation (about 

 four months) there have been two periods of 

 extremely rapid division, the rate rising to five 

 divisions in twenty-four hours and continuing 

 at this rate for six or seven days. During 

 these periods no individuals with four or five 

 vacuoles were seen and the two-vacuoled forms 

 seldom passed into the three-vacuoled condi- 

 tion before division, although they did not lose 

 the power of returning to the higher numbered 

 vacuoled state when the division rate slowed 

 down. 



The original laboratory culture was started 

 by Dr. Merkle Jacobs in the fall of 1914. The 

 paramoecia he had been using in high tempera- 



ture experiments were thrown into a battery 

 jar of hay infusion. So far as is known, the 

 animals used for these experiments had the 

 normal number of contractile vacuoles, though 

 there is a possibility that the higher number 

 were already present. The irregularity of the 

 behavior of the extra contractile vacuoles would 

 seem to indicate that they were recently ac- 

 quired structures that had not become as yet 

 firmly established as a part of the organism. 

 There has also been some slight indication 

 lately, observed by both Dr. Jacobs and myself, 

 of a tendency to settle down into a more reg- 

 ular order with three as the maximum num- 

 ber of vacuoles. 



Since Paramecium caudatum has been the 

 most widely studied protozoan and no cases 

 have been reported where extra contractile 

 vacuoles have been found, considering the 

 origin of the culture, there is some excuse for 

 suggesting that this potentiality for extra 

 vacuoles may have been acquired. The great 

 irregularity of the time of formation of these 

 vacuoles along with the tendency to become 

 more regular, as stated above, would seem to 

 bear this hypothesis out. The paramoecia of 

 the original culture had been subjected to a 

 temperature of at least 40° Centigrade and it 

 might be supposed that the extra vacuoles were 

 formed under the stress of the unusual envi- 

 ronment. Furthermore, Dr. Jacobs has found 

 that this race is abnormally resistant to high 

 temperatures. Under the conditions where 

 ordinary race of paramoecia are killed at tem- 

 peratures of 40° Centigrade to 42° the race in 

 question will survive an exposure to 44° or 

 more. 



A more extended account will be published 

 shortly giving more of the details and methods. 

 It is intended later to attempt to develop a new 

 multi-vacuoled race by subjecting normal indi- 

 viduals to high temperatures in order to test 

 the hypothesis suggested above. 



Dr. Jacobs has carried on experiments with 

 the same race of Paramcecium which have con- 

 firmed those recorded here. 



Egbert T. Hance 



Zoological Laboratory, 

 University op Pennsylvania 



