EARLY DEVELOPMENT OF GRAFFILLA. IS; 



form in which to work out the history and significance of the 

 aborting spindle, for owing to the viviparous mode of repro- 

 <lu< -lion prevailing in this species it is quite impossible to secure 

 a complete series of stages showing the different steps. One 

 (,ui not he at all certain that it occurs in every egg, though the 

 frequency at which it is met would indicate that it did. Ne\er- 

 thele , it would seem that some rather important function 

 -hould he aligned to the aborting spindle; for it- appearance in 

 -ome do/en different species of flat worms niu-t exclude it from 

 the category of abnormal behavior. It i- therefore hoped that 

 an oppori unity may be offered to work out it- history in detail 

 in a !a\orahle form, such as one of the o\ipan>u- species from 

 \\hich a -eries of stages can be secured from the uteru-. 



J, / '.inatiini. By insemination is usually meant the act 

 ot introducing the spermatozoa into the egg. In ('>raflUla the 

 process curs during the last stages of yolk ah-orption \\hilc 

 tin- formative capsule is still attached to the ovary, and consists 

 in the introduction of spermatozoa into tin- cap-ule. The in- 

 M ininaiin- organ is the modified, or bifurcated part <>l the uteru-. 

 In 1 is -hown a beautiful case. The -ection passes through 



the di-tal end of the uterus, and the left-hand lohe of ihat or^an, 

 tilled \\ith -pennatozoa, is in direct contact with the hinucleated 

 i ap-ule. Any number of similar fign n he demon-iraied 



in the preparations, so that no doubt can exisl regarding ihe 

 interpretation which we have placed upon Mich picture-. It 

 \\milil -eem that the uterus took an acti\e part in the pn- 

 of in-eminaiiin. Linton reports an ob-er\ aiim \\hich points 

 to the -ame < ' inclusion. 



This method of insemination must necessarily permit a numher 

 f -permaii>/oa to get into the capsule, hut o\\in- to their -mall 

 -i/e thev are soon lost among the yolk granules, so that an 

 enunu-ration of them is impossible. S- > far as one can tell the 

 -perm- di. not at first invade the immeiliate neighborhood of 

 the two nuclei, but remain in the peripheral portion of the cap- 

 Mile, and later penetrate the egg- a -lion time before the begin- 

 ning of maturation. 



4. Maturation. As in the case of all ova accompanied by the 

 proce of feriili/ation. those of Gratfilhi throw off t\\o polar 



