SUMMARY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(principally invertebrata and cryptogamia), 



MICEOSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 

 a. Embryology.! 



Development of Motor Nerve-Trunks and Myotomes in Lepido- 

 siren.J — J. Graham Kerr concludes from a study of a series of early 

 stages that the facts of development in the motor nerves of Lepidosiren 

 give strong support to the view that the nerve-trunk is not a secondarily 

 formed bridge between spinal cord and motor end organ. The motor- 

 trunk can be traced back to a simple protoplasmic bridge, which already 

 connects the substance of the medullary tube with that of the myotome 

 at a stage when they are still in contact. As regards the origin of the 

 protoplasmic sheath, the evidence of Lepidosiren is equally emphatic. 

 At an early period the motor-trunk is perfectly naked. At a certain 

 stage masses of mesenchymatous protoplasm laden with yolk become 

 applied to the nerve-trunk, gradually spreading over the whole of it. 

 As development goes on the yolk becomes used up, the protoplasm with 

 its nuclei extends into the substance of the nerve-trunk — doubtless to 

 keep up the proper proportion between the bulk of the nerve-trunk and 

 its nutritive surface in contact with the sheath protoplasm. The proto- 

 plasm itself becomes less and less conspicuous, and eventually is only to 

 be detected in the immediate vicinity of the nuclei. Lepidosiren offers 

 no evidence, so far, as to the ultimate origin of the nerve-fibrils. They 

 appear gradually in an at first simple protoplasmic matrix. The paper 

 contains also an account of the development of the myomeres. 



Influence of Constant Agitation on the Development of the 

 Toad's Egg.§— T. H. Morgan has devised an apparatus which excludes 



* 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, 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. 



X Trans. Roy. Soc. Edinb., xli. pt. 1 (1904) pp. 119-28(6 pis.). 



§ Ana . Anzeig., xxv. (1904) pp. 94-6. 



