SUMMARY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(principally invertebrata and cryptogamia), 



MICBOSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 



a. Embryology. f 



Variation : Germinal and Environmental.^ — J- Cossar Ewart uses 

 the phrase germinal variation for the variation which inevitably flows 

 from the blending of two highly specialised germ-cells ; all the varia- 

 tions in the germ-cells up to the moment of conjugation, together with 

 the variations during development and growth, are referred to as en- 

 vironmental variations. 



Environmental variation is considered under several heads. (I.) 

 There are those environmental variations which occur during develop- 

 ment, e.g. dwarfing and arrestments ; and it is pointed out that many 

 are " congenital," but neither inherited nor transmitted. (H-) There 

 are environmentally produced changes occurring from the end of de- 

 velopment to the end of the reproductive period, including changes in 

 the germ-cells during their growth and maturation, (a) None of his 

 results favour belief in the transmission of acquired somatic variations ; 

 on the contrary, some of them indicate that such transmission is highly 

 improbable. (b) There is evidence of the influence of nutrition and 

 somatic well-being on the germ-cells, (c) There is some evidence that 

 age, seasonal condition of parents, &c. influence the progeny : thu=, as 

 a female increases in age and vigour her germ-cells may increase in 

 prepotency, (d) The influence of the age of the parents, and of the 

 ripeness of the germ-cells, is then illustrated. Some interesting evidence 

 is adduced to show that inter-breeding is a cause of variation. Mating 

 before and after the normal time is also provocative of changes, some of 

 which (in rabbits, &c.) seem to occur with some degree of definiteness. 



* 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 ol 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. 



+ This section includes not only papers relating to Embryology properly so called, 

 but also those dealing: with Evolution, Development, Reproduction, and allied subject?. 



X Scient. Trans. R. Dublin Soc, vii. (1901) pp. 353-78. 



