ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 33 



malities in development, such as spina bifida in various degrees. 

 Deteriorative effects are also predominantly seen in the spinal cord, the 

 eyes, and the muscle-plates. These vary greatly in amount. There 

 may be slight displacements in the brain, or there may be general 

 disruption of the tissues. 



Oogenesis of Zoogonus mirus.* -F. Wassermann gives a detailed 

 account of the oogenesis in this Trematode. He especially discusses the 

 origin of the reduced chromatin elements, the early displacements of 

 the chromatin, and the maturation divisions. His results neither prove 

 nor disprove the theory of the continuity of the chromosomes. "Nor is 

 he able to convince himself of the applicability of the " hetero-homceo- 

 typic reduction-scheme " to the maturation divisions in this type. It 

 does not seem probable that the first maturation division is a reduction 

 division, and the second is certainly an equation division. 



Development of Ear Ossicles in Foetal Perameles.f— R. W. Palmer 

 finds evidence that the manubrium of the malleus is a secondary and 

 later developed process of the malleus, that the tympanic is a triradiate 

 bone, that the quadrate and incus are homologous, and that the Mam- 

 malian tympanic bone is the modified angular of the Reptiles. 



Early Development of Scale and Feather.}— Joseph Schleidt finds 

 that the scales on the chick's feet have primordia like those of Reptilian 

 scales. On the trunk of the grass snake and of the chick, and on the 

 feet of the chick, there are very similar structures, small bilaterally 

 symmetrical papillae, passing without definite limits into one another, 

 and forming what Ficalbi described as an " ondulazione in toto." They 

 consist of a proliferation of epidermis and dermis. When feathers are 

 going to develop there is on the second day a proliferation of epidermis 

 at the apex and steep side of the papillae, and the feather primordia 

 become circumscript as if the " ondulazione in toto " was smoothed out. 



The foot of the chick and the fore limb of the blackbird show 

 embryonic down-feathers on scales. At a very early stage the down- 

 primodia are seen as special differentiations on the scale primordia. The 

 author inclines to the conclusion that there is not an homology between 

 scales, embryonic down-feathers, and definitive feathers. 



Development of Pharyngeal Bursa in Ferret.§— Marion Radford 

 concludes from her observations that the anterior end of the notochord, 

 i.e., Sessel's pocket, loses connexion in the ferret embryo with the main 

 chorda, which at this stage ends blindly close to the pharyngeal wall ; 

 and that this anterior portion develops characteristics which would 

 point _ to its identity with the pharyngeal bursa as described in human 

 and pig embryos. 



* Arch. Mikr. \nat., lxxxiii. 1913) 2te Abt., pp. 1-140 (4 pis. and 43 figs.). 



t Anat. Anzeig., xliii. (1913) pp. 510-15 (4 figs.). 



X Arch. Mikr. Anat., Ixxxiii. (1913) lte Abt., pp. 118-29 (1 pi.). 



§ Anat. Anzeig., xliv. (1913) pp. 371-7 (6 figs.). 



Feb. 18th, 19 U D 



