722 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
opinion should tend toward the wider acceptation of the whole “ Urmund ” 
theory. 
Ectodermic Origin of the Cartilages of the Head.* — Miss J. B. Platt 
gives a preliminary notice of her investigations on this point. She has 
studied the conditions found in Necturus , which, on account of the size 
of the cells and the differentiation of ectoderm and endoderm produced 
by differences in the quantity of yolk, is an especially favourable object. 
She emphasizes the importance of proliferations from the ectoderm in 
the formation of the rudiments of cartilage, and the consequent difficulty 
of grouping the tissues collectively known as mesoderm with the two 
primitive germ-layers. 
Development of Hose and Upper Lip.f — Dr. F. Keibel sides with 
Hochstetter against His in regard to certain facts in the development of 
these structures. In cat, guinea-pig, pig, and man the nasal cavity is at 
an early stage a blind sac. At this stage, therefore, there is no groove 
connecting the primitive mouth-cavity with the primitive nasal cavity. 
The “ Choane” arises secondarily, as Hochstetter has described. The 
first rudiment of the primitive palate arises from the apposition of 
the lateral and the median nasal process, and not from the apposition 
of the latter and the maxillary process. The latter union takes place 
subsequently in the formation of the upper lip. The author recognizes 
the importance of the recent work of His on human and animal physio- 
gnomy, but, taking a somewhat broader comparative survey, comes to 
different conclusions on many points. 
Mammalian Spermatogenesis. J — Mr. J. E. S. Moore points out the 
closeness of the parallel which exists between the spermatogenesis of 
Echinoderms, as formulated by Field, and a spermatogenetic scheme 
which he has elaborated for the Mammalia. He finds in the spermatozoa 
of Mammals — 
(1) The chromatic portion of the nucleus enclosed in a transparent 
case probably composed of paranuclein and linin. 
(2) A portion of the spermatid “ Nebenkern ” derived from the little 
wart on the nuclear membrane, kytoplasmic in origin. (1) and (2) form 
the head. 
(3) Two centrosomes, which with the head form the cephalic portion. 
(4) A further portion of kytoplasm, which forms the tail. 
The relations of the parts of an Echinoderm spermatozoon are shown 
in the next table : — 
Nucleus 
Centrosome 
“ Nebenkern ” 
Cell-membrane 
Kytoplasm 
| Head 
| “ Mittelstiick ” 
Cephalic 
portion. 
Tail. 
Human Tails.§ — Dr. J. J. Pjatnizky discusses “the structure of a 
human tail and human tails in general.” He has gathered together the 
* Anat. Anzeig., viii. (1893) pp. 506-9. f Tom. cit., pp. 473-87 (2 pis.). 
% Tom. cit., pp. 683-8 (4 figs.). 
§ Inaug. Diss., 2. verbess. Aufl., Moskau, 8vo, 1893, 89 pp., 2 pis. (Russian) ; 
Anat. Anzeig., viii. (1893) pp. 583-4. 
