58 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
hedgehog, and man, point clearly to dimorphism. From Sertoli’s cells 
there arise by amitosis long, sometimes coiled, chromatin-containing 
axial filaments, with a terminal swelling and a plasmic mantle. These 
may be (a) parts of spermatozoa, i.e. tails, or ( b ) rudimentary (abortive, 
reduced) spermatozoa. The author adopts the latter alternative. He 
has also some suggestions to offer in regard to the embryonic hermaphro- 
ditism of the epithelial content of the testes, and compares the penetration 
of the spermatozoa into the protoplasmic mass of Sertoli’s cells with 
fertilisation. He emphasises his conclusion that the axial filament is 
formed, not from the chromatin of the nucleus, but essentially from the 
centrosomes. 
In a subsequent paper * the author recognises that the tail-rudiments 
which he confesses to have confused with dimorphic Nebenformen , do 
not arise from cells different from those which form the heads. They 
arise from the centrosomes, accessory body, and cytoplasm of the 
spermatids ; the axial filament in particular is formed mainly from the 
central corpuscle. 
Path of the Spermatozoa in the Frog.f — Herr 0. Frankl has 
studied this subject by means of injections from “ Leydig’s duct,” and by 
fixation of the organs in frogs killed during copulation. Both methods 
showed that the vasa efferentia are continued through the kidney as 
transverse canals opening into the urospermatic duct, and that these 
transverse canals are connected by sagittal ducts with the Malpighian 
capsules. Although therefore the Malpighian capsules are not in tho 
direct path of the spermatozoa, yet a rise of pressure, produced e.g. by an 
extremely active flow of semen temporarily blocking the ducts, forces 
spermatozoa into the cavities of the capsules. The paper concludes 
with a brief discussion as to the relations of sexual and excretory organs 
in Fishes and Amphibia. 
Prof. M. Nussbaum J points out the morphological interest of the 
fact that in adult males of Bana esculentci var. berolinensis and hungaricci 
the efferent canals from the testes are connected with renal canals whose 
glomeruli persist, while in B. fusca the glomeruli in the same region 
have disappeared. 
Problems of Hybridisation. § — M. Andre Suchetet, who has devoted 
so much attention to hybridism, asks three questions : — (1) What is the 
nature of those species which can be successfully crossed ? (2) Are their 
progeny fertile or sterile ? (3) What are the causes of the sterility of 
many ? 
(1) Authentic cases of hybridism in Mammals number about 93, of 
which 82 (a) are crosses of species of the same genus; there are 11 
doubtful cases (6) of hybridism between members of different genera ; 
there is no instance of crossing (c) between members of distinct families 
or widely separated genera. Among birds, 262 cases are recorded, 178 
of the first category (a), 68 of the second ( b ), and 16 (some doubtful) of 
the third (c). 
(2) Of the 82 crosses between Mammals of distinct species but of 
* Anat. Anzeig., xiv. (1897) pp. 145-7. 
f Zeitschr. wiss. Zool., lxiii. (1897) pp. 23-38 (1 pi.). 
X Zool. Anzeig., xx. (1897) pp. 425-7. 
§ Journ. Anat. Physiol., xxxiii. (1897) pp. 326-55. 
