174 ARTHUE E. SHIPIiET. 



fertilising the eggs of the ripe female Lampern, hatching the 

 larvse out, and rearing them in confinement. The breeding 

 time is during the latter half of April and the beginning of 

 May. 



The generative products of both male and female were 

 squeezed into glass vessels containing fresh water, and the 

 contents slightly stirred. The eggs at once adhered to the 

 bottom and sides of the vessel, and were left undisturbed for 

 three or four hours. The water was then poured oflF and a 

 fresh supply added. This was kept thoroughly aerated by 

 means of Semper^s aerating apparatus. The number of eggs 

 fertilised were about 70 per cent, of the total, though some 

 hatches were much more successful than others. The rate of 

 segmentation and development also varied greatly, being 

 influenced by the temperature and manner of aeration. The 

 unfertilised eggs very soon could be distinguished from the 

 fertilized ; they developed great cavities or craters and were 

 soon attacked by fungi. The fungus, however, rarely afl'ected 

 the developing eggs. 



The spermatozoa have elongated heads, pointed at their free 

 end, but thicker at the end from which the tail arises (fig. 1). 

 Their length is from 35 to 40 micro, mm., of which the head 

 forms 3 micro, mm. They move actively about in the water 

 until they come into contact with an ovum. They enter the 

 egg through a micropyle, and Calberla states that the head 

 only enters the protoplasm of the ovum, the tail remaining 

 fixed in the micropyle, thus hindering the entrance of other 

 spermatozoa. 



The eggs are almost spherical, with a diameter of about a 

 millimetre. On contact with water the outer cell-membrane 

 swells up and forms a gelatinous coating, by means of which 

 the eggs adhere to the bottom and sides of the vessel. This 

 gelatinous envelope is of considerable thickness ; it ultimately 

 disappears shortly before the embryo is hatched. Sections 

 through unfertilised eggs show the protoplasm crowded with 

 oval yolk granules, which stain deeply. These yolk granules 

 vary in size, and this is very evident in the segmenting eggs. 



