764 
SUMMARY OP CURRENT RESEARCHES RELATING TO 
Glyptodon has prismatic back teeth of triconodont type, it is likely that 
of the biconodont back teeth of modern Edentates the posterior at least 
have arisen by the reduction of triconodont forms. According to Rose 
the difference between molars and premolars depends on the number of 
single conical teeth which have coalesced in either case. 
Enamel Organ in Edentate'** — Dr. E. Ballowitz describes in the 
embryo of Dasypus the presence of a distinct enamel organ, as previously 
noticed by Tomes and by Pouchet and Chabry. But Ballowitz has 
discovered that it is more than embryonic ; a portion — the lower margin 
— persists as an epithelial ring at the base of the pulp-papilla. As it 
lies at the area whence the tooth continues throughout life to grow, it 
may be that the formation of the dentine involves the co-operation of 
the enamel organ. Of its great importance the author is confident. 
Apical Spot in Embryos of Swimming Birds. f — Herr A. Klinc- 
kowstrom has found in embryos of Sterna hirundo , Larus canus , L. 
marinus , L. glaucus , and Anser brachyrhyncJms , an “ apical spot ” which 
lies a little behind the top of the pineal outgrowth, “on that part of the 
head-surface towards which the pineal body is directed before its 
follicular modification begins.” On this spot, before there is any rudi- 
ment of feather-papillae, the epidermis is differentiated as a slight 
elevation which becomes pigmented. A cupola-like protrusion is 
formed, which subsequently seems to be divided into two. In the 
middle of this protrusion the epidermis proliferates and forms several 
thin sagittal ridges. Finally, in the corium a mass of pigment accumu- 
lates and forms the “ apical spot.” Subsequently it more or less com- 
pletely disappears. Is it a constriction of the pineal apex, or an 
integumentary structure which has only secondary relations with the 
pineal body ? Is it a homologue of the frontal spot of Anura or com- 
parable merely to the pineal scale of reptiles ? To the last interpretation 
the author inclines. 
Origin of Pigment in Bnfo.} — Herr F. Winkler finds that the 
pigment is present in the ova from the first. During development it is 
formed by a modification of yolk-plates. It occurs in all three layers, 
but especially in ectoderm and endoderm. In all the actively formative 
cells it increases in the protoplasm. For the young embryo at least, its 
origin cannot be the result of a modification of haemoglobin. 
Leptocephalidse.§ — SS. G. B. Grassi and S. Calandruccio give a 
preliminar statement of their observations on the metamorphosis of 
Leptocephalidae into Muraenidae of which they are the normal larvae. It 
has been experimentally proved that Leptocephalus morrisi, L. punctatus , 
and another form not described are the larvae of Conger vulgaris; that 
L. diaphanus is the larva of Congromursena balearica ; L. Kollikeri of 
Congromursena mystax ; L. Kefersteini of Ophichthys serpens. 
Abnormal Segmentation. || — Dr. E. 0. Straehley describes the 
remarkable absence of nuclei in artificially fertilized ova of the trout. 
* Arch. f. Mikr. Anat., xl. (1892) pp. 133-56 (2 pis.). 
f Zool. Jahrb., v. (1892) pp. 177-83 (1 pi). 
X MT. Embryol. Inst. K. K. Univ. Wien, 1892, pp. 64-80. 
§ Atti (Rend.) R. Accad. Lincei (1892) pp. 375-9. 
[] MT. Embryol. Inst. K. K. Univ. Wien, 1892, pp. 20-2. 
