A11T[F1C[.\L PAUTHENOGENESrS AND FERTILTSATION. 495 



sea water were fertilised with spermatozoa^ which were 

 treated with a "05 per cent, solution of potassium hydrnte 

 until only a few were mobile. While polyspermy occurred in 

 more than half the eggs, the remainder were fertilised by a 

 single spermatozoon. In these cases, however, the sperm 

 nucleus did not unite with the germ nucleus, but the aster 

 became detached from it, and advanced alone to the germ 

 nucleus, a bipolar figure was formed and division proceeded. 

 The sperm nucleus took no share in the process, but passed un- 

 altered into one of the blastomeres. Later, however, either in 

 the two- or the four-cell space, it broke up into its chromosomes, 

 which entered into the equatorial plate of the cell in which it 

 was included, and which now divided like its neighbours. 

 Such eggs were capable of developing to the blastula stage. 



The question presented itself: Was this aster and the 

 amphiaster the result of the activity of an ovocentrum, or 

 were they the product oF the sperm aster? 

 . In monospermic eggs Teichmann found the early stages 

 very scarce, and, though very suggestive, too few for absolute 

 proof, and the phenomena seen in dyspermic eggs ai-e 

 described to fill the gap. It may be admitted that in these 

 eggs, in spite of the apparent inactivity of the sperm nucleus, 

 the sperm aster Avith its centrum is the operative factor in 

 starting the developmental process. The appearances are 

 very similar to those in the etherised eggs described by 

 Wilson (1901). In that form, as in Echinus, the nuclei con- 

 jugate when they are very unequal in size, and before the 

 division of the aster. In Asterias and other forms an amphi- 

 aster is developed before conjugation, and the nuclei are 

 nearly equal in size. In the experiments the union was 

 delayed, as in " partial fertilisation," and the amphiaster was 

 formed before the conjugation. 



Among 'J'eichmann's observations I shall refer only to those 

 of monospermic eggs. The main feature is the detachment 

 of the sperm aster from its nucleus, its application to the egg 

 nuclens, and its normal division, followed by normal segmen- 

 tation. The fate of the sperm nucleus depends on the 



VOL. 46, PART 3. — NEW SERIES. H H 



