noted that Baer's principle of explanation of double monsters 

 was subsequently completely confirmed, especially when it was 

 found that this kind of formation could be obtained experi- 

 mentally by pretwisting the ova, turning the vegetative pole 

 upwards, effecting temperature changes, and so on. 



In subsequent years Baer from time to time returned to 

 teratological questions, describing interesting cases he 

 discovered. The following cases present information of this 

 nature : 



1. "A new case of twins joined at the forehead, and 

 comparison of it with analogous cases. "8 This concerned 

 accreted twins, aged about eight months of uterine life, 

 prepared for the Academy's collection. Both the foeti are 

 female, well developed, joined to each other obliquely. Baer 

 noted that similar kinds of union of accreted twins are seen 

 more frequently in birds than in mammals and cited corresponding 

 references. 



2. "Notice sur un monstre double vivant "9 This case 

 is that of a monster which attracted Baer's attention because 

 the accreted double was delivered at full term and was born 

 alive. The position of the twins was completely symmetrical, 

 in contrast to the previous case, where they were at angles 

 to each other , 



3. "Remarks on blind fish, an example of delay of develop- 

 ment. "10 In these remarks Baer described a carp [Cyprinus 

 gibelio) caught in a muddy pond in Kolomyaga. The eyes of the 

 fish were rudimentary and sealed under the skin. In connection 

 with this Baer posted the question, can darkness be the cause 



of underdevelopment of the eyes? 



8. Baer, "Neuer Fall von Zwillingen, die an Stirnen verwachsen 

 sind, mit ahnlichen Formen vergliechen. Mit einer Tafel," 

 BULL. PHYS.-MATH. ACAD. SC. ST. PETERSB. (1845), 



3, No. 8, pp. 113-128. 



9. Baer, "Notice sur un monstre double vivant, compose de deux 

 enfants f eminins , " IBID. (1856), 14, No. 3, pp. 34-37. 



10. Baer. "Ein Wort liber einen blinden Fisch als Bildungs- 



Hemmung," BULL. ACAD. SCIENCES (1862), 4, pp. 215-220. 



460 



