578 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Thyroid and Thymus of Amphibians.* — Dr. H. Bolan has investi- 
gated the occurrence and structure of these organs in a large number 
of Amphibians. There may be one thyroid or several on each side, 
and the content consists either of colloid vesicles or of a connective- 
tissue mesh work with imbedded leucocytes and blood-vessels. There 
seems no regularity in their occurrence, for nearly related forms are 
often different. There is, however, never more than one colloid gland 
on one side. In Ecaudata the gland is always single, and it is colloid 
except in Molge rusconii. The author leaves the mutual relations of 
the two kinds of glands an open question. 
In Ecaudata and Caudata the thymus is single on each s : de, except 
in the larval form of Amblystoma tigrinum, which has a variable number. 
In Siphonops there are four in a line. The content is a connective- 
tissuo meshwork with leucocytes in the meshes, besides Hassal’s cor- 
puscles and sometimes fine capillaries. 
Non-cellular Structures-! — Herr Boris Sukatscboff has studied the 
minute anatomy of such non-cellular ^structures as the cuticle in various 
animals, sponge-fibres, &e. Among the more important results are the 
following. The cuticle of Lumbricus in surface view showed the numer- 
ous pores of the skin-glands, and in optical section was seen to be com- 
posed of many layers. 'These layers are not fibrous, but have a fine 
foam structure. Chemically the cuticle consists of albuminoid substance. 
In Aulastomum and Hirudo the cuticle consists of a single layer, which 
careful examination shows to have a foam structure. Pores are present 
as in Lumbricus. In both Hirudo and Aulastomum the surface of the 
cuticle is marked by areas corresponding to the underlying cells. The 
same condition exists in the carapace of Gammarus , which is many- 
layered and exhibits irregularly arranged spaces (foam structure). A 
detailed study of old cocoons of Nephelis shows that the walls are formed 
from a foam-like coagulum of an originally soluble substance. The cocoon 
substance both in Hirudo and Nephelis gives the proteid reactions and 
is an albuminoid. 
Structure of the Cell. — Prof. W. Flemming,! in his presidential 
address to the “ Anatomische Gesellschaft,” gives a general historical 
account of the observations made on the minute structure of the cell ? 
from those of Frommann in the seventies until the present day. From- 
mann was the first to describe fibrillar structure both in living proto- 
plasm and in stained preparations. Owing to imperfect methods and 
instruments, he fell into some errors which were corrected by Flemming 
at the beginning of the next decade. Almost at the same time Klein 
described a fibrillar structure which he called the cellular network, his- 
description agreeing in essentials with that of Flemming. Heitzmann 
also described in different cells a fibrillar framework, but maintained 
that the interfibrillar substance is of purely fluid nature, and that the 
fibrils are identical in structure with the nuclear granules. Both these 
statements are strongly contested by Flemming. Passing over the 
observations of Van Beneden, Carnoy, and Leydig, which in essence 
* Zool. Jahrb., xii. (1899) pp. 657-710 (11 figs.). 
+ Zeitschr. f. wiss. Zool., lxvi. (1899) pp. 377—106 (3 pis. and 1 fig ). 
+ Anat. Anzeig. (E>ganzungsheft), xvi. (1899) pp. 2-12. 
