SUMMARY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(principally invertebrata and cryptogamia), 



MICEOSCOPY, Etc.* 



ZOOLOGY. 



VEETEBEATA. 

 &• Embryolog-y.t 



Entrance of Spermatozoon into the Egg.} — Jacques Loeb discusses 

 the nature of the conditions which determine or prevent the entrance 

 of the spermatozoon into the egg. If eggs of Stronyylocmtrotus pur- 

 puratus or Arbacia are induced to develop by the methods of artificial 

 parthenogenesis, a spermatozoon can enter the egg or an individual 

 blastomere. This shows that the block caused by the entrance of a 

 spermatozoon must be due to a change not necessarily identical with that 

 inducing the development of the egg. The block to the entrance of 

 heterogeneous sperm is rapidly reversible, and confined to the surface 

 of the egg or the spermatozoon, or both. In the case of the ovum of 

 Strong ylocentrotus and the sperm of Arbacia (and many similar instances), 

 the specific block can be overcome by a slight increase in the alkalinity 

 of the sea-water. The change brought about by the hyperalkaline sea- 

 water is rapidly reversible. 



It has been shown that when the unfertilized eggs of S. purpuratus 

 are treated for a couple of hours with hypertonic sea-water, those of 

 certain females develop parthenogenetically, while those of others do not. 

 Perhaps those that develop parthenogenetically are those in which the 

 hypertonic sea-water can induce the cortical changes underlying the 

 membrane formation. Whatever the nature of the individual difference 

 may be, the eggs of S. purpuraius that have been induced to develop 

 into larvre by a hypertonic solution can be fertilized with sperm while 



* The Society are not intended to be denoted by the editorial " we," and they 

 do not hold themselves responsible for the views of the authors of the papers 

 noted, nor for any claim to novelty or otherwise made by them. The object of 

 this part of the Journal is to present a summary of the papers as actually pub- 

 lisJied, and to describe and illustrate Instruments, Apparatus, etc., which are 

 either new or have not been previously described in this country. 



t This section includes not only papers relating to Embryology properly so 

 called, but also those dealing with Evolution, Development, Reproduction, and 

 allied subjects. 



J Amer. Nat., xlix. (1915) pp. 257-85. 



