ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
37 
fall into the blood-cavity, and the venous wall is formed afresh by a 
simple epithelium. There is a complete parallelism between the wealth 
of the blood in the leucocytes and the formation of the thickenings of 
the venous wall. It is probably due to an increase in size of the venous 
plexus by the formation of buds, which become connected with the 
neighbouring buds and are ultimately hollowed out. The cells of the 
paraplacental tissue have a phagocytic function. In the later periods 
of gestation the epithelium which invests the uterine cavity undergoes 
the modifications which have been described by M. Van Beneden. 
Embryo of Platypus.* * * § — Messrs. J. P. Hill and C. J. Martin publish 
a full account of their observations on a Platypus embryo from the 
intra-uterine egg.j" They raise our hopes in stating that, as they now 
know the exact breeding season of Platypus in certain convenient 
localities in New South Wales, they are going to endeavour to obtain 
the stages intermediate between the earliest we now possess and the 
embryo described in the present paper. The authors’ abstract was so 
full that it will suffice if we now content ourselves with referring the 
student to their details. 
A Strange Enclosure in a Hen’s Egg4 — Herr W. v. Nathusius de- 
scribes a remarkable body from a hen’s egg which contained cartilage, 
bone, and connective tissue. After bringing together a number of other 
cases of a similar nature, he gives a detailed description of the enclosure. 
It is most to our purpose, however, to give prominence to his suggestion 
or conclusion that the body owes its origin to a double-yolked or twin 
ovum which has developed parthenogenetically and abnormally, and given 
rise to something comparable to an ovarian cyst in Homo. 
Gastrulation in Xteptiles.§ — Dr. E. Mehnert agrees with Kupffer and 
others that gastrulation in Reptiles is introduced by an invagination of 
the upper germinal layer. The invaginated sac lies at first freely 
between the upper germinal layer and the paraderm. Later, however, 
its lower wall fuses with the lecithoderm (paraderm), and a perforation 
of the archenteron ( TJrdarmdurclibruch) follows. Some say that the dis- 
appearance of the lower wall of the archenteron with the associated 
lecithoderm is due to the gradual increase of one originally small aper- 
ture ; others describe numerous perforations. Mehnert cites twelve de- 
scriptions by various authorities, and concludes, from his study of JEmys , 
&c., that perforation at one spot is the normal process, and that the 
appearance of numerous holes is artificial. 
Degeneration of Tissue in Tadpole’s Tail.|| — Dr. W. Noetzel has 
studied this from a pathologist’s point of view. His results tend to 
weaken the general belief in the importance of leucocytes in the reduc- 
tion of the tail. 
The skin. The cutis membrane is invaded by connective-tissue cells 
of the subcutis, and becomes fibrous connective-tissue continuous with 
the subcutis. As the tail shortens the epidermis thickens; its cells 
* Proc. Linn. Soc. N.S.W., x. (1895) pp. 43-74 (5 pis.). 
t See this Journal, 1*95, p. 409. 
X Arch. f. Mikr. Anat., xlv. (1895) pp. 654-92 (1 pi. and 15 figs.). 
§ Anat. Anzeig., xi. (1895) pp. 257-69. 
|| Arch. f. Mikr. Anat., xlv. (1895) pp. 475-512 (1 pi.). 
