( 201 ) 

 SUMMARY 



OP CUKBENT RESEARCHES RELATING TO 



ZOOLOaY AND BOTANY 



(principally Tnvertehrata and Cryptogamia), 



MICROSCOPY, &c., 



INCLUDING ORIGINAL COMMUNICATIONS FROM FELLOWS AND OTHERS.' 



ZOOLOGY. 



A. GENERAL, including Embryology and Histology 

 of the Vertebrata. 



Development of tlie Optic and Olfactory Organs of Human 

 Embryos.f — A, KoUiker has had the opportunity of examining four 

 human embryos, the smallest and youngest of which was 8 mm. long and 

 4 weeks old, the largest and oldest 21 mm. and 8-9 weeks. The 

 earliest had the lens-pit still open, and the two layers of the secondary 

 optic vesicles were not fused ; the proximal of these layers consisted 

 of at least two layers of cells, and showed in its anterior two-thirds 

 fine, round, and proportionately large pigment-granules, and there was 

 a double limiting membrane ; the distal or retinal layer consisted of 

 subequal elongated cells, arranged in from four to six layers, its limit- 

 ing membrane passed directly into the upper of the above-mentioned 

 limiting membranes of the pigment-layer. The lens appeared to 

 consist of two or three layers of elongated cells, while the epidermis 

 was uni-laminate. The vitreous body had the appearance of a well- 

 developed transparent layer richly provided with cells ; these were all 

 stellate or spindle-shaped. Sections of the hinder regions showed 

 that the choroidal fissure advanced from below and forwards. 



In the next embryo the lens was constricted off, though in size 

 that embryo was only 8" 5 mm. long; in some points it showed an 

 advance, and in others it lagged behind the rather smaller embryo, so 

 that it seems that the early developmental stages of the eye vary 

 somewhat in rapidity. After describing the characters of this 

 rudimentary organ the author gives a very useful enumeration of the 

 seven well-observed cases of eyes in embryos not exceeding 8 • 5 mm. ; 

 he then passes to the third embryo, in which the lens- substance is 



* The Society are not to be considered responsible for the views of the 

 authors of the papers referred to, nor for the manner in which those views 

 may be expressed, the main object of this part of the Journal being to present a 

 summary of the papers as actually published, so as to provide the Fellows with 

 a guide to the additions made from time to time to the Library. Objections and 

 corrections should therefore, for the most part, be addressed to the authors. 

 (The Society are not intended to be denoted by the editorial " we.") 



t Verb. Phys.-med. Gesell. Wurzburg, xvii. (1883) pp. 229-57 (4 pis.). 

 Ser. 2.— Vol. IV. P 



