34 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Pronephros of Lepidosteus.* — Dr. J. Beard finds in unhatched or 
newly hatched embryos of Lejpidosteus osseus that the pronephros pre- 
sents on each side three outer and three inner ciliated funnels. The 
three outer open into the general body-cavity, the three inner into a 
capsule, which represents a shut-off portion of the body-cavity. Into 
the capsule there projects from the under side of the aorta a long folded 
glomerulus, made up of small and large lappets. At a later stage the 
number of outer and inner funnels becomes reduced to two on each side ; 
and it should also be noted that to begin with there are suggestions of 
five or six. The author discusses the resemblances between Amia, Lepi- 
dosteus , and Acipenser as regards the pronephros; Lepidosteus is less 
reduced as to its funnels, and therefore, in this respect, more primitive 
than Amia, but whether the pronephros of Acipenser is really the most 
primitive of the three, as Jungersen would have it, can hardly as yet be 
decided. 
Metamorphosis of the Attraction-sphere in Spermatogonia of 
Salamander.j — Dr. F. Meves describes in great detail how the attraction- 
sphere in the spermatogonia of Salamandra maculosa breaks up at the 
end of summer into a mass of granules, out of which it is reconstituted in 
spring. He distinguishes a medullary and cortical zone in the sphere, and 
describes its normal state as well as that of the nucleus and the cell- 
substance. The change is first seen in the form of the sphere, which 
becomes irregular with small tubercles. Then it breaks up into a 
number of separate bodies, roundish, oval, concavo-convex, or otherwise 
in form. These separate in the cell-substance and break up into smaller 
portions. They come to surround the nucleus, and cease to be homo- 
geneous, becoming granular. Meanwhile the nucleus also changes, 
becoming cleft and “ polymorphic,” and the cytoplasm becomes looser in 
structure. Reverse processes occur in spring. In a number of testes 
fixed in spring, Herr Meves was able to detect an elimination of nuclear 
and even nucleolar substance. 
The author thinks that the metamorphosis of the sphere chiefly 
affects the cortical zone, and that the medullary zone possibly remains 
intact. But the intricate process remains enigmatical. The elimination 
of nuclear material is possibly comparable to a “ reduction karyogamique.” 
j 8. Histology. 
The Central Corpuscles.! — We should have given an earlier notice 
of Prof. M. Heidenhain’s great paper on central corpuscles and their re- 
lations to nucleus and cytoplasm, but the magnitude of the task has 
delayed us. The cells investigated were lymphocytes and the giant cells 
of the medulla of bones, for it appeared safer to make an exhaustive 
study of these two types, than to attempt more diffuse investigation. 
The first chapter deals with the microcentrum. The resting cell 
has at least two centrosomata, though by over-differentiation of the 
* Anat. Anzeig., x. (1894) pp. 198-201. 
f Arch. f. Mikr. Anat., xliv. (1894) pp. 119-84 (5 pis.). [This journal now 
changes its title to ‘ Archiv fur Mikroskopische Anatomie und Entwicklungs- 
geschichte.’J 
X Arch. f. Mikr. Anat., xliii. (1894) pp. 423-758 (7 pis.). 
