382 



SCIENCE 



[N. S. Vol. LI. No. 1320 



sionally called "Dark" Absidia will serve as 

 a convenient example. The collection of this 

 species consists of 40 races. They have been 

 contrasted with one another by twos in watch- 

 glass cultures and all the possible combina- 

 tions have been made as shown in the table. 

 Grades A to D were assigned to the different 

 strengths of sexual reaction measured by the 

 number of zygospores produced in a given 

 contrast. Each race was given a final numer- 

 ical grade made up of the average of its re- 

 actions with all the other races and the races 

 were arranged in the table according to their 

 final grading. The plus and minus races were 

 placed in series by themselves. There was no' 

 reaction when a plus was contrasted with an- 

 other plus nor when a minus was contrasted 

 with another minus. Whether they were of 

 equal sexual vigor or one was weak and the 

 other strong, the result of contrasting two 

 races with the same sign was always negative. 

 The collection of races therefore seemed 

 dimorphic so far as sex is concerned. A race 

 was either shown to be plus or minus or showed 

 no reaction in a given combination and was 

 provisionally classed as " neutral." There 

 were no races evident that could be called sex 

 intergrades. Albert F. Blakeslee 



Carnegie Station tor 

 Experimental Evolution 



(To be concluded) 



AN ANALYSIS OF AIM AND INCENTIVE 

 IN A COURSE IN GENERAL ZOOLOGY 



INCENTIVE AND AIM 



That an incentive is necessary for the ao- 

 complishment of work is a postulate that 

 needs no discussion. A review of my work 

 as a teacher has led me to investigate the 

 incentives that activate my students — mostly 

 freshmen plimged into a course in general 

 zoology. I have felt for some time that the 

 aim of the course did not furnish an in- 

 centive for work. 



Aim is confused with incentive because in 

 some cases the two are equivalent. Aim is an 

 aspiration for an ideal while incentive is an 

 earthly motive. The statement of an aspira- 



tion may form an incentive for a few; but 

 for most students the aim is soon forgotten. 



INCENTIVE OP students IN GENERAL ZOOLOGY 



Since the motive that actually completes 

 the work is not the aim, it is worth while to 

 inquire what is the incentive. I recognize 

 that the material with which I have to do 

 shows a great deal of individual variation. In 

 this " population " four classes can be dis- 

 cerned. 



1. Those who work because the aim fur- 

 nishes the incentive. In a so-called " general 

 cultuie " course this is indeed a small class ; 

 in a technical school, however, the condition 

 is reversed. 



2. Those who work because of love for the 

 subject, another small class. Although in 

 some students this desire is inborn and prob- 

 ably hereditarj', yet the proportion can be 

 raised by an inspiring teacher. 



3. Those who work for rewards. Our in- 

 stitutions, in their wisdom, through years of 

 experience, have devised gTades and honors. 

 Some students have an inborn and probably 

 hereditary ambition to seem better than their 

 fellows and so react to this stimulus. Indeed 

 competition can furnish a splendid incentive. 



4. Those who work through fear. The 

 same machinery erected to appeal to the am- 

 bitious reacts to prod the laggard. Under 

 the threat of probation, condition, and ex- 

 clusion, the victim struggles on. This is a 

 large class and, in some ways, the most inter- 

 esting. Although this group contains the 

 dullards, yet the ranks are far from being 

 homogeneous — the most brilliant member of 

 the class may be buried in its ranks. 

 How often have we seen a student, who, by 

 constant threats, has just managed to scramble 

 through our course, enter a technical school 

 and not only lead his class but in time his 

 profession. Lack of incentive is the key to 

 his attitude toward the course in zoology. 

 Being a more reasoning being than his fellows 

 who work for love or rewards, and, feeling 

 that the aim did not furnish an incentive, he 

 gave his energies where, to his mind, results 

 would be of more value. 



