8 G. O. Sars. 



the blastoshperes 1 ), will not shrink on being transferred to 

 pure oil of cloves, in which they very soon acquire sufficient 

 transparency to be examined both externally and dioptrically 

 by slightly shifting the focal distance of the objective. The 

 usual transference into Canada Balsam may also now be easily 

 effected; but the clearness of detail is thereby somewhat 

 diminished, and I have therefore preferred to examine 

 the ova when still in oil of cloves. 



Miss Bonnevie has kindly assisted me in the difficult 

 attempt to make sections of these diminutive objects by 

 imbeding a number of prepared and stained ova in paraffine and 

 then cutting the whole mass by the aid of the microtome. 

 Though the sections thereby acquired were somewhat 

 defective, they have been useful to me for the purpose of 

 controlling the observations made from intact ova. The fig. 

 14 on PI. 2 has been made by a combination of several of 

 these sections. 



The account of the embyronal development given be- 

 low does not lay any claim to be an exhaustive descrip- 

 tion. It has only been my purpose in this paper to state 

 the more essential features, and to direct the attention of 

 more experienced embryologists to the subject. 



The accompanying plates have been prepared in the 

 autographic manner, and may, I hope, sufficiently answer 

 the purpose here intended. 



J ) The outer hyaline capsule will, by this proceeding, be reduced 

 to a slight film, which will not essentially interfere with a closer 

 examination of the true ovum. 



