^32 LILIAN SHELDON. 



the egg-shell before placing the eggs in spirit, as otherwise it 

 collapses and crushes the embryo. Before cutting sections of 

 the eggs I almost always removed the shell, since it was too 

 hard to cut well, and was also apt to prevent the paraffin from 

 penetrating the ovum. 



Within the shell the ovum is enclosed in a vitelline mem- 

 brane, which adheres closely to it, and is thin and membranous. 

 The two are easily distinguishable in eggs stained with picro- 

 carmine, as the shell stains yellow and the vitelline membrane 

 red. 



The only accounts which have been hitherto published of 

 the development of P. novae-zealandise are by Hutton^ and 

 Kennel/ both of which are very brief. These observers state 

 that the segmentation is holoblastic, which is not the case, it 

 being rather on the centrolecithal than on any other type of 

 segmentation. 



Methods. 



The most satisfactory preparations obtained were from eggs 

 which were preserved in hot or cold corrosive sublimate and 

 glacial acetic acid mixed in the proportion of two to one. Other 

 ova were preserved in Kleinenberg's picric acid, but these were 

 not satisfactory. The eggs were all stained in picrocarmine, 

 and afterwards passed through the various strengths of alcohol 

 in which a small amount of picric acid was dissolved ; by this 

 method the yolk is stained yellow, the protoplasm light, and 

 the nuclei deep red, so that they are easily distinguishable 

 from one another. I am indebted to Mr. Harmer for the 

 knowledge of this method. 



The embryos were all removed from the uterus in the living 

 state, and were preserved at once. 



I do not purpose in this paper to enter into the subject ot 

 the ovarian ovum and the changes undergone by it in its 



' Hutton, Capt. F. W., "On Peripatus novse-zealandise," 'The 

 Annals and Magazine of Natural History,' 4tli Series, Nov., 1876. 



' Kennel, Dr. T., " Entwickluugsgeschiclite von P. Edwardsii, Blanch, 

 und P. torquatus, n. sp.," ' Semper's Arbeiten,' Band vii, 1885. 



