1889.] Embryology. 645 
of the embryo and the egg envelopes. This space is filled with the 
coarsely granular secretion which before revolution filled the cavity of 
the amnion. The glairy secretion of the invaginated appendage stains 
pink in borax-carmine, and is distinctly marked off from the amniotic 
In Nepa the secretion of the pyramidal cells differs from that in 
Cicada in a remarkable manner. The tapering ends of the cells are 
very delicate and transparent, and the secretion from the tip of each 
cell is not confluent with the secretion from the neighboring cells to form 
a glairy mass as in Cicada, but assumes the shape of a thread fully as 
long as the cell which secretes it, and protrudes into the space between 
the body wall and the ^^^ envelopes. As the secretion of each cell 
remains thus independent, the secretion of the whole organ strikingly 
resembles a brush or a bundle of cilia. 
I conclude that the ///vaginated bulbous bodies in the first abdominal 
segment of Hemiptera are the homologues of the ^vaginated bulbous 
appendages in other insect embryos from the following facts : 
1. These organs in Hemiptera are two in number, and appear only 
in the first abdominal segment, in positions held by the evaginated 
appendages in other insect embryos. 
2. They are ectodermic in their origin, like the appendages in other 
3. They have the same shape and cytological structure as the 
evaginated appendages of the first abdominal segment in Orthoptera 
and Coleoptera. 
It is obvious that the invaginated appendages of the Hemiptera 
could never have functioned as gills, and their complete similarity in 
minute striicture to the protruding bulb-shaped or even lamellar ab- 
dominal appendages of embryo beetles is strong evidence against 
(Iraber's and Ayer's supposition that these organs are respiratory in 
the forms heretofore studied. 
On the other hand the supposition of Patten and myself that these 
organs are glandular, receives strong confirmation from my observa- 
tions as briefly given above. My observations also make more plaus- 
ible the supposition that the lung hooks of scorpions and spiders are 
the homologues of evaginated appendages. 
I reserve a more complete and illustrated description of \w\ results 
for future publication.— W. M. Whkf.ler, Public Museum, Mih.'aukcc. 
Observations on the Placentation of the Cat.— The follow- 
ing preliminary notes are offered in advance of the publication of an 
illustrated paper on the same subject. 
