The elements of embryology. / By M. Foster ... and Francis M. Balfour.

  • Michael Foster
Date:
1874
Catalogue details

Licence: Public Domain Mark

Credit: The elements of embryology. / By M. Foster ... and Francis M. Balfour. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    C. Removal of the blastoderm. Vide VI. C. Witli the imincubated blastoderm still'greater care is required in removal than with the 20 hours' blasto- derm, and there is no special advantage in doing so unless it is intended to harden it with osmic acid. D. Sitrface view tra7isparent from above. ■ Observe the absence of the central opacity. E. SiLrface view transpai^ent from tmderneath. Nothing further to be observed than from above. F. As an opaque object. There is nothing to be learnt from this. G. Sections. Manipulation as in YI. G. Only one section is required, viz. one taken through the centre of the blastoderm, shewing: a. The distinct ejnhlast h. The loiuer layer cells not as yet differentiated into mesoblaet and hypoblast. c. The thickened edge of the blastoderm. d. The segmentation cavity and formative cells. ■ VIII. Examination of the process of Segmentation. To observe the process of segmentation it will be found necessary to kill a number of hens which are laying regularly. The best hens lay once eveiy 24 hours, and by observing the time they usually lay (and they generally lay pretty regularly about the same time), a fair guess may be made beforehand as to the time the egg has been in the oviduct. By this means a series of eggs at the various stages of seg- mentation, may usually be obtained without a great unnecessary sacrifice of hens. For making sections, the yolk must in all cases be hardened as a whole, which may be done as recommended in VI. G.