436 Miscellaneous. 



of the male protoplasm through the membrane at the point where 

 this is directly in contact with the female protoplasm— that is to say, 

 at the apex of the cumulus. 



The protoplasmic cone uniting the membrane with the vitellus 

 soon detaches itself from the membrane and reenters into the vite - 

 line mass. By employing coloui'ing substances the e^g then pre- 

 sents three nuclei, two situated near one pole of the egg, the other 

 at the opposite pole. Of the former two, the superficial one is the 

 nucleus which, by dividing, forms the polar globules ; the other, 

 more deeply seated, is the female pronucleus ; the nucleus formed 

 at the opposite pole, which is at first superficial, is the male pro- 

 nucleus, which, starting from the point where the cumulus of 

 fecundation was situated, directs itself towards the centre of the 

 egg to meet with the female pronucleus, with which it enters into 

 conjugation to form the first nucleus of segmentation. I do not think 

 that the nucleolus of the male pronucleus can be regarded as the 

 unmodified head of a spermatozoid. 



It seems to me that the numerous sperraatozoids fixed upon the 

 membrane of the egg, and which appear to have no function, are 

 not quite without infiuence on the act of fecundation. The gyratory 

 movement which they give to the egg, a movement so easily 

 detected in the Echinodermata, the Ascidia, and a great many other 

 animals, perhaps assists in favouring the progress of the two pro- 

 nudei towards the centre of the egg. I have frequently remarked 

 that the eggs which had not turned for a certain time were deve- 

 loped irregidarly, and sometimes even did not enter into embryonic 

 evolution. 



Is the existence of a cumulus of fecundation peculiar to the 

 Echinodermata? Prof, de Lacaze-Duthiers, in his splendid mono- 

 graph of Dentalmm, figures in the egg of that mollusk a mamilla 

 situated at the pole opposite to the polar globules, and which may 

 perhaps have the same signification as the cumulus of the urchin. 

 However the eminent zoologist declares that he could not say 

 whether this mamilla is visible before the arrival of the sper- 

 matozoids. 



In the common starfish the cumulus of fecundation is more diffi- 

 cult to see than in the urchin ; but, on the other hand, the polar 

 globules are much more apparent, and their production presents 

 more clearly the picture of a cell-division with unequal products. — 

 Comptes Hendus, April 9, 1877, p. 720. 



Obitimry. 



John Leckenby, Esq., F.G.8., F.L.S., died at Scarborough on the 

 7t}i of April, 1877, in the 63rd year of his age. He was an excel- 

 lent and zealous naturalist, and desei-vedly possessed the esteem of 

 all his numerous friends and correspondents. Yorkshire has lost in 

 him one of her best men of science. Mr. Leekenby became a con- 

 tributor to the ' Annals ' in 1858 ; and his last communication was 

 made, in conjunction with Mr. Marshall, in December 1875. He 

 also published papers on local geology in the ' Quarterly Journal of 

 the Geological Society' and the ' Geologist ' in 1859. 



