ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
6L 
tion of the girdle arise by intercalation or excalation of pre-sacral 
segments, by slipping of the girdle upon the column towards the head or 
towards the tail, or by some other means ? (2) Is there any correlation 
between the variations of the plexus and those of the girdle, and if so, 
of what sort is it? To the first question the author answers, after dis- 
cussion, that neither intercalation, nor escalation, nor slipping is involved ; 
the abnormal position of the girdle represents development of a new 
girdle at a new point, usually to the tail end of the normal. To the 
second question the author answers that the nerve relations show that 
variations of girdle and plexus are nearly parallel, but that they are in 
some degree independent, as exhibited by the fact that the strength- 
centre of the plexus does not have just the same relation to the girdle in 
the variant that it had in the normal condition. 
Pedigree of Vertebrata.* — Herr 0. Jsekel discusses the origin of 
paired limbs, the possible characters of the vertebrate Stamm form, and 
the relationships of the various classes. He expresses his concep- 
tion of the phyletic relations in the following scheme (slightly modi- 
fied) : — 
Aves 
Reptilia 
Mammalia 
Amphibia 
Teleostei 
Ganoidei 
Stegocephali 
Dipnoi 
Placodermi 
Acanthodi 
Elasmobranchii Older Ostracodermi 
-Protochordata 
SB. Gcs. Nat. Freunde Berlin, 1896, pp. 107-29. 
