119 



Omittiug the doubtful cases (indicated by ? in the above table) 

 we find that supernumerary molars occur eight times in the lower 

 jaw as against seven times in the upper. It is further shown that 

 these extra teeth occur more frequently on the left than on the right 

 side. It is particularly interesting to observe that in all cases the 

 extra tooth is added to the posterior end of the series. No writer 

 has described the occurrence of a supernumerary cheek-tooth inter- 

 calated in any part of the dental series. 



The significance of these supernumerary teeth may be open to 

 question ; but I incline to the view that they are examples of an 

 excessive development of dental germs, and not of reversions to an 

 ancestral condition. There seem to be too weighty objections to any 

 other view. 



References. 



1) Magitot, E., Traite des anomalies du Systeme dentaire, Paris 1877 

 PI. 5, Fig. 9. 



2) Hensel, R., Ueber Homologien und Varianten in den Zahnformeln 

 einiger Säugetiere. Morph, Jahrb., Bd. 5, 1879, p. 542. 



3) Bradley, 0. Charkock, On two Cases of Dental Anomaly. Journ. 

 Anat. Phys., Vol. 36, p. 356. 



4) Bateson, W., Materials for the Study of Variation, London 1894, 

 p. 245. 



5) Hates, M. H., Veterinary Notes for Horse Owners, 6. Edit., London 

 1903, p. 752, Fig. 210. 



6) Bateson, W., On numerical variation in Teeth, Proc. Zool. Soc, 

 London, 1892, p. 102. 



7) Salensky, W., Equus Przewalskii Pol. Wissenschaftliche Resultate 

 der von N. M. Przbwalski nach Central-Asien unternommenen Reisen, 

 Bd. 1, Abt. 2, Lief. 1, 1902. 



Nachdruck verboten. 



Untersuchungen über die Reifung- und Befruchtung des Eies 



Ton Cymhulia Peronii. 



Vorläufige Mitteilung 

 von A. Nekrassoff (Moskau, Zoologisches Museum). 



Mit 16 Abbildungen. 



Während eines zweimaligen Aufenthaltes an der Russischen 

 Zoologischen Station in Villefranche-sur-mer, im Frühling 1902 und 

 1903, hatte ich Gelegenheit, Material für eine Untersuchung des 

 Reifungs- und Befruchtungsprozesses des Eies von Cymbulia Peronii 



