. 
52 FRANK A. HAYS 
Wright (p. 306) states that in his poultry-breeding operations he 
does not expect normal size or vigor in offspring from cocks used 
on too many hens, and further (p. 131), that cocks that are used 
on too many hens show the effect in that the eggs fertilized by 
them show signs of hatching but do not hatch because the em- 
bryos fail in many cases to reach full development. Pusch (15, 
p. 182) expresses the almost universal belief in this matter, 
though he does not consider the idea well grounded when he 
writes: “Braucht man die’ Deckhengste, wie tberhaupt jedes 
miénnliche Zuchttier, zu stark, so schidigt man nicht nur deren 
Begattungs- und Befruchtungsvermégen, sondern auch die 
Qualitat ihrer Nachzucht; deshalb wird die Stutenzahl fiir wert- 
volle Vollbluthengste auch nur auf 30-40 Stiick bemessen und 
die zu bedeckende Stute erst durch den Probierhengst auf ihre 
Rassigkeit hin gepriift.”’ Day (18, p. 219) expresses the belief 
that excessive use of the boar is likely to result in small, weak 
litters of pigs. 
Just why sperm cells that are produced by a male in heavy 
sexual service should produce inferior offspring when they take 
part in fertilization is not clear. Can it be possible that the 
genetic makeup of the spermatozoa is changed by heavy service? 
Is it not possible that any sperm cell possessing life, however 
depleted and weak it may be, will carry into the egg a potentiality 
of full vigor? Or, on the other hand, can we conceive of differ- 
ent degrees of vital force in a sperm cell? Since all of the activi- 
ties of the animal body are so beautifully coérdinated, it would 
appear very rash to assume without conclusive evidence that 
males under natural breeding conditions would derange any vital 
function, such as reproduction, by continuing to copulate after 
the reproductive system was producing an abnormal product. 
As has been pointed out in our first paper (Lloyd-Jones and 
Hays, 717), there appears to be a relation between the number of 
services performed by the male and the fertilizing power of his 
semen, but as far as we have been able to measure, we are led to 
believe that only a slight change can Be brought about by this 
treatment. Pusch (15, p. 182) states that in Oldenburg, stal- 
lions are often allowed to make from four to six or even eight 
