288 E. C. FAUST. 



occurs more than is desirable. In the head of the spermatozoon 

 no inner chromatic rod is differentiated from the cytoplasmic 

 envelope. Moreover, it often takes several days to measure a 

 considerable number of individuals, so that temporary prepara- 

 tions, such as those obtained with aceto-carmine, are objection- 

 able. For this same reason intra vitam staining was abandoned. 



For the most of the preparations Delafield's haematoxylin was 

 used and proved much more successful than Schneider's aceto- 

 carmine. The testis was taken out of the individual and placed 

 in normal salt solution. It was then transferred to a slide that 

 had been previously coated with a thin film of albumen fixative. 

 The spermatozoa were teased out on the slide and examined in a 

 drop of some fluid, such as Ringer's, to determine their motility 

 or non-motility. After most of the solution had been allowed to 

 evaporate so that only a bit of moisture was left around the 

 spermatozoa, the preparation was fixed in osmic fumes for thirty 

 seconds and then stained in Delafield's haematoxylin. This 

 method was found to give a maximum number of straight 

 spermatozoa with an inner chromatic rod well differentiated. 



The microscope used in the measurements was equipped with 

 a Leitz 2 mm. oil immersion objective and Zeiss compensating 

 oculars. A large number of individuals was measured and a 

 curve of variability plotted. In every individual it was the 

 length of the inner chromatic rod which was determined. A 

 description of this chromatic rod occurs later under the descrip- 

 tion of a mature spermatozoon. 



2. Sources of Error. The probable sources of error that need 

 special consideration are (i) imperfect technique in preparations; 

 (2) immaturity of the spermatozoa; or (3) incorrect measure- 

 ment. 



(i) Error Due to Imperfect Technique in Preparations. Several 

 smears of mature spermatozoa were prepared by the aceto- 

 carmine method. Measurements made from them were not 

 uniform, due to faulty technique. Many of the sperm heads 

 had been curled or shrunken in fixation. Lack of an exact tip 

 or base of the chromatic rod could have given rise to an error 

 of from 1^1 to 5/x in measurements of length. Distention and 

 distortion were common. On account of the faulty prepara- 



