INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 555 



vesicle. Brandt is also of opinion that the blastoderm owes its origin 

 to the germinal vesicle ; lie says that the protoplasm of the blasto- 

 derm corresponds to the germinal vesicle, and the contained nuclei to 

 the germinal spot. 



Dr. Bobretzky agrees with the latter in his general results, inas- 

 much as he finds in two species of Lepidoptera which he specially 

 examined, that (1) previous to the formation of the blastoderm, morpho- 

 logical elements having the value of true cells, appear in the yolk ; 

 (2) some of these gradually pass to the surface, where they form the 

 blastoderm ; while (3) others remain in the yolk, and, later on, bring 

 about the formation of the so-called yolk-spheres, which are likewise 

 to be regarded as true cells. The author was not, however, enabled 

 to observe the connection of these cells with the germinal vesicle ; 

 and he is still in opposition to Brandt, and in agreement with the 

 great majority of observers, in regarding this structure as the true 

 nucleus of the ovarian cell. As to the blastema of Weissmann, its 

 existence is denied by Brandt, and was never observed by Bobretzky, 

 unless, as he says, the perij^heral vitelline layer represents it ; but this 

 takes no share in the formation of the blastoderm. 



The author rightly insists on the necessity of extended and com- 

 parative investigations before deducing any generalizations ; and he 

 points out that, in a spider," elements have been observed by Ludwig 

 very similar to those found by him in the egg of the Lepidoptera. As 

 to the cleavage in these latter, he points out that as the protoplasmic 

 elements are not all used up in the formation of the blastoderm, they 

 so far diifer from what has been observed in the Crustacea and 

 Arachnida, where the cleavage is complete ; but he explains that he is 

 of opinion that the above-mentioned yolk-spheres do ultimately go to 

 form the endoderm, while he believes that the blastoderm really cor- 

 responds to the ectoderm. In connection with other observations 

 lately made, it is of interest to observe that the mesodermal bands 

 begin to be segmented some time before the ectoderm. 



Mode of Recognition among Ants.* — The Eev. H.C. McCook has 

 made experiments upon two species of ants (" Pavement " Ant — 

 Tetramorium ccespitum, and Pennsylvania Carpenter Ant — Camponotua 

 Pennsyh- aniens) as to their mode of recognizing each other and distin- 

 guishing fellow-formicarians from those of alien nests, with whom they 

 at once fight when they meet. 



It occurred to him that this recognition was based upon a certain 

 odour which, in different degrees of intensity, is emitted by the respec- 

 tive factions ; or, which seems less likely, upon the presence in the 

 individuals of the combatants of two distinct odours. This degree of 

 odour, or difference in odour, he supposed might be dependent upon 

 some temporary difference in the physical condition, age, or environ- 

 ment of the antagonists. Supposing that there were any basis of truth 

 in this theory, it further occurred to him that the presence of an arti- 

 tificial and alien perfume of sufficient strength to neutralize the dis- 

 tinctive animal odours or degrees of odour, and environ the combatants 



♦ 'Proc. Acad. Nnt. Sci. Phila.,' 1878, p. 15. 



