OKLAHOMA ACADEMY OF SCIENCE 41 



tapeworms and 20 hook worms. It is not an uncommon occur- 

 rtnce to remove from 300 to 400 worms from a single chicken. 

 Most flocks of sheep in the state are infested more or less with 

 stomach worms. In some flocks every animal is infested and the 

 losses among lambs are often serious. Hogs are generally infested 

 with worms, as are horses. This applies to the state as a whole. 

 Chicken flocks arc nearly all more or less severely affected. Thus 

 we may have some idea of the prevalence of parasitism in our 

 state. We have many species and many times the infestation is 

 very heavy, not only with internal parasites but also with external 

 forms as well. 



The tendency is toward an increase in parasitism as the en- 

 vironment becomes more contaminated with eggs and larval worms 

 by being inhabitated with various animals. Thus we must be on 

 the alert and guard against any possible chances for increase by 

 instituting sanitary measures to prevent the spread of such diseases. 

 The appeal that it is hoped the foregoing remarks will bring forth 

 is, that we many have more interest in this field and more workers 

 to bring this matter before the public. The public must be informed 

 in order that it might know of methods of keeping down parasitic 

 infection and lessen chances for parasitic diseases. 



XX. A PRELIMINARY REPORT ON THE OPTIC TRACT 



OF EYELESS FLIES 



Mildred Hoge Richards and Esther Y. Furrow. 



From the Zoological Laboratory of the University of Oklahoma. 

 Contribution No. 17, Second Series. 



Among the many mutations which have occured in the fruit 

 fly, Drosophila mclanogastcr, one of the mcst interesting is that 

 known as "eyeless." Eyeless, a condition in which the compound 

 eyes are much reduced in size or altogether lacking, was first ob- 

 served by Mildred Hoge Richards, in 1914 and has been bred ever 

 since as a distinct race. This character was at once found to be 

 definitely heritable and the gene responsible for it was located in 

 the fourth chromosome. 



There is considerable variation in the ^character of eyeless flies. 

 .'\. fly may have no eyes at all, two very small eyes, or one larger 

 and one smaller eye. By selection Dr. T. H. Morgan has recently 

 increased the percent of totally eyeless flies. 



The present problem is concerned with the internal structure 

 of the optic tract of this race, with the idea of determining how 

 much of this optic tract is lacking in eyeless. Heads of normal 



