SUMMARY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(PRINCIPALLY INVERTEBRATA and cryptogamia), 



MICEOSCOPY Etc.* 



ZOOLOGY. 



VERTEBRATA. 

 a. Embryolog-y.t 



Artificial Parthenogenesis.* — Prof. Jacques Loeb showed, in 1899 

 and 1900, that, by au increase iu the osmotic pressure of the sea-water, 

 the unfertilised eggs of a number of Echinoderms can be caused to 

 develop parthenogenetically. He has since found that the unfertilised 

 eggs of Chsetojiterus behave similarly, and may be developed to the 

 stage of trochophore larvae. In no case did he see a single egg of the 

 control material develop into a larva, though some showed a beginning 

 of segmentation. The greatest precautions were taken to exclude the 

 possibility of spermatozoa getting among the eggs. 



The Chsetopterus eggs are able to develop parthenogenetically if 

 they are put for about one hour into one of the following solutions, 

 and then into normal sea-water : — 



15-20 21 n NaCl + 85 sea-water. 



40 2 % cane-sugar + 60 ., 



30 2i n MgCL + 70 



10 5~ n CaCC + 90 



All these solutions have one element in common, the approximately 

 equal increase of the osmotic pressure. It seems, therefore, justifiable 

 to assume that the increase in the osmotic pressure, or the loss of water 

 on the part of the egg, is the cause of the parthenogenetic develop- 

 ment of these eggs. KC1 (or perhaps the K-ions) seems to possess a 

 specific effect. There is no warrant for supposing that the eggs of 

 Chsetopterus are normally parti lenogenetic, or that the animals experi- 

 mented with were dichogamous hermaphrodites. 



The unfertilised eggs cannot develop into trochophores if left in 

 normal sea-water, but a small number of K-ions is sufficient to cause 



* 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 published, and to 

 describe and illustrate Instruments, Apparatus, &c, 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. 



X Amer. Journ. Physiol., iv. (1901) pp. 423-59. Cf. this Journal, 1900, p. 61. 



