April, '101 COTTON : LOW TEMPERATURE APPARATUS 141 



problems, and, what is more promising of results, they are usually 

 provided with ample funds to secure the special apparatus needed in 

 their work. 



At the Tennessee Station we have one of these problems and for 

 the solution of certain phases of it we soon discovered that apparatus 

 for securing and maintaining constant low temperatures was essen- 

 tial. A careful search through the catalogs of both domestic and 

 foreign firms dealing in laboratory supplies convinced us that there 

 was nothing on the market to satisfy our particular needs. Incu- 

 bators and other devices for securing and maintaining constant tem- 

 peratures above the melting point of ice were listed by all of them 

 but nothing for temperatures below that point. We then set to work 

 to devise and construct a piece of apparatus for this purpose, which, 

 because of the intense interest expressed by those who have seen it 

 in an incompleted condition and its wide applicability to biologic 

 problems, it has seemed advisable to describe at this time. 



Our particular problem concerned itself with the North American 

 Fever Tick and the effect of low temperatures upon the various 

 phases of its life cycle. We know that a certain low temperature is 

 fatal to all engorged adult ticks under a given set of conditions and 

 also that a lower temperature under another set of conditions will 

 not seriously aft'ect them. Why? What are the governing factors 

 and under what conditions do they act ? We know that low tempera- 

 ture inhibits egg laying. What is the critical temperature for this 

 function? Ever since the successful application of the law of accu- 

 mulated effective temperatures to the boll weevil problem, there has 

 been a demand from those engaged in tick investigation work for a 

 similar law relating to the fever tick. Mr. Hunter's paper entitled 

 *'A Tentative Law Relating to the Incubation of the Eggs of Mar- 

 garopus annulatiis," which was presented before this Association two 

 years ago, was an attempt to satisfy that demand. Recently we have 

 attempted to apply this law to the immense mass of data accumulated 

 at the Tennessee Station during the past three years, but I cannot 

 flatter myself that we have achieved any great success. The trouble 

 is that the upper and lower limits are too far apart and the excep- 

 tions too many and too serious. There seem to be some controlling 

 factors which we have not yet mastered. What are they? These 

 are all questions of vast importance from an economic point of view 

 and moreover questions that must be answered if we are to know the 

 fundamental laws on which to base a more successful scheme of tick 

 eradication. 



Various investigators have felt the need for low temperature con- 



