ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
517 
have any vital significance. There can be little doubt, for example, that 
the ‘ orange spot ’ which forms such a striking feature of the egg of an 
Elasmobranch in its early stages, has been handed down with little 
change from Palaeozoic times.” The author does not confirm Hoffmann’s 
discovery (in Acanthias) of an invagination cavity and open blastopore ; 
at the corresponding stage in Heterodontus there was only the segmenta- 
tion-cavity, which in one case had been opened by an artificial rupture. 
Passage of the Eye in a Flat-Fish.* * * § — Mr. T. Nishikawa has made 
an interesting observation on the young form of an undetermined species 
of flat-fish. The dorsal fin had grown forward before the rotation of the 
right eye, but the anterior extension had not united with the head, and 
had left a distinct hole. Through this hole the right eye passed, travel- 
ling dorsally and to ,the left. “ If we compare this mode of passage of 
the eye with the first mode described by Agassiz, which is undergone 
by the majority of flat-fishes, we find little difference between them, 
beyond the fact that before the rotation of the eye takes place, the dorsal 
fin grows forward to the snout and lies in apposition with the head, 
leaving a hole for passage. If the hole had been obliterated before the 
rotation of the eye, a hole would have had to be pierced, as observed in 
Arnoglossus by Ehrenbaum and in Plagusia by Agassiz.” In every case 
the passage of the eye from one side to the other is morphologically 
along the dorsal surface of the head ; but the case described is, as to mode 
of passage, intermediate between what occurs in the majority and what 
occurs in the two genera named above. 
Ovum in Testis of Lamprey .| — Dr. R. H. Ward describes the occur- 
rence of a characteristic ovum in an actively functioning testis of the 
lamprey. In the lobule occupied by the ovum the mother-sperm-cells 
had apparently suffered an arrest of development ; in other parts they 
had formed spermatozoa and had almost entirely disappeared. They 
persisted in this lobule, which was otherwise comparatively empty of male 
products. “Was the nourishment just here unsuited to them, or was it 
so appropriated by the ovum that enough was not left for them ? ” 
Liver and Pancreas in Ammoccetes.^ — Dr. A.Brachet discusses the 
various views which have been expressed in regard to the development 
of liver and pancreas in Ammocoetes, and gives an account of his own ob- 
servations. From these it results that Ammocoetes, and probably all the 
Cyclostomata, should be placed between the lancelet on the one hand 
and the Selachians and higher Vertebrates on the other. In Ammocoetes 
the hepatic caecum of Amphioxus has become a true liver, but the pan- 
creas, though indicated by an Anlage or rudiment-zone on the intestine, 
is not yet isolated as a special gland. 
Development of Heart in Petromyzon.§ — S. Hatta has observed 
that the heart, which is always found, independent of age, in the same 
section of the body as the pronephros, arises as a single endothelial tube 
formed from mesenchymatous cells between the two primary layers at 
the point on the ventral median line where the head-fold joins the larger 
* Annot. Zool. Japon., i. (1897) pp. 73-6 (2 figs.), 
t Araer. Mon. Micr. Journ., xviii. (1897) pp. 213-7, 
X Anat. Anzeig., xiii. (1897) pp. 621-36 (6 figs.). 
§ Journ. Coll. Sci. Imp. Univ. Japan, x. (1897) pp. 225-37 (1 pi.). 
