EFFECTS OF INJURY UPON SPERM. 225 



may be of more frequent appearance than my notes indicate. 

 Again it may be possible that such cases are sometimes present 

 in eggs fertilized with normal sperm. I have no reason to believe 

 that my control cultures contained such cases. 



(i) The rate of development in the experimental cultures 

 often proved to be very irregular and was usually slower than 

 that of the controls. For example, when the controls first have 

 definite setse the experimental cultures have none. Segments 

 are marked out earlier in the controls. Early cleavage planes 

 are often delayed, but this may be due in some part to the failure 

 of the weakened sperm to reach the egg as soon as it should. 

 But it seems certain that, even allowing for this fact, the early 

 stages are somewhat retarded in development. 



(j) In practically every experiment the controls lived longer 

 than the experimental cultures and the death rate in them was 

 not so much as one tenth as large. Although an effort was made 

 to keep the controls under exactly the same conditions as the 

 others there were usually fewer larvae in the experimental dishes 

 (presumably a more favorable condition). Old eggs and organic 

 materials were removed so as to eliminate any possible toxic 

 action of products of decay. In some cases the water was 

 changed from day to day but with little effect. It seems that 

 the normal animals in the controls are able to withstand the 

 artificial conditions incident to life in the laboratory for a much 

 longer time than those in the experimental cultures, which are 

 so weakened by the injury to the part which comes from the 

 male parent, that they cannot exist under such conditions as are 

 provided. 



(k) The trochophore stage seems to be a difficult one to pass. 

 It frequently happens that this stage is permanent. In some 

 cases at about the time when segments should be marked out 

 and setae should appear, the animal becomes irregular in form or 

 swells up and becomes transparent, due probably to the absorp- 

 tion of water. In some cases the trochophore remains in its 

 original condition without change. In most cases death takes 

 place soon after elongation should take place but I have often 

 kept the permanent trochophores for a day or more after they 

 should have elongated. 



