554 SUMMARY OF CURRENT RESEARCHES RELATING TO 



from a germarium, and not from an ovarian epithelium ; and that the 

 yolk is formed by cell-degeneration and not by secretion. The embryo 

 exhibits a primitive segmentation, before the appearance of the 

 permanent segments, each of the seventeen of which bears a pair of 

 appendages, though some are rudimentary and deciduous. The dorsal 

 vessel arises as a paired organ, the lateral halves of which give rise, by 

 fusion, to a median tube, just as in some Vermes ; the blood-corpuscles 

 are the nucleoli of endodermic cells. A rather startling discovery is 

 that of the gills, which Ayers describes as a pair of lateral outgrowths 

 derived from the ectoderm of the pleural region of the first abdominal 

 segment ; the gill-cavities are continuous with the body-cavity, and they 

 appear to serve as channels through which the vascular fluid circulates. 

 " The gill-pad is essentially a single-layered sac, with a much- 

 constricted neck, evaginated from the pleural region of the abdomen "; 

 they are not tracheate gills, for they contain no nuclei. 



The author failed to observe any sharp distinction between a cell 

 and its nucleus, or between a nucleus and a nucleolus ; but he was 

 able to detect the existence of segmental enlargements of the meso- 

 dermic somites, similar to those from which the nephridia of worms 

 take their origin. 



The author discusses the origin and function of the embryonic 

 membranes (amnion and serosa), and points out that an answer is 

 impossible if we do not clearly comprehend the relations of the 

 embryo to its nutriment and food-yolk. They can hardly be supposed 

 to have been primitively protective in function, and the egg is fur- 

 nished with a protecting membrane (the chorion) before it leaves the 

 body of its parent. Ayers comes to the conclusion that the serosa 

 functions as a yolk-sac, while the amnion is the dorsal wall of the 

 insect. It is to be noted that in Limulus the serosa does become a 

 " vicarious chorion " (Packard), and after the splitting of the true 

 chorion, forms a protective membrane. 



The egg-parasite Teleas appears to be remarkable for the absence 

 of embryonic membranes, and to give rise to a " larval form intermediate 

 between the blastosphere and the cyclops-larva of Ganin." 



Origin of Bees' Cells.* — Dr. Donhoff urges objections to the 

 views of Buffon, carried further by Miillenhoff, that bees' cells are due 

 to pressure, pointing out that there is no relation between the forms 

 of the cells and of the bees' bodies, and that he has observed a single 

 female build a nest consisting of a number of six-sided cells ; further, 

 the diflference seen in cells formed by bees and drones cannot be 

 correlated with any differences to be found in the inhabitants; in 

 the formation of the queens' cells by other bees there is no pressure 

 to produce the rhomboid pits ; direct observation of the formation 

 of a comb was not rewarded by any indications of pressure ; no 

 reasonable amount of pressure on the walls of cells seems to have any 

 effect in altering their form. 



The author thinks that Darwin has erred in supposing that the cells 



* Arch. f. Anat. u. Physiol., 1&84, Physiol. Abth,, pp. 158-5. 



