674 THE GENERATIVE ORGANS. 
302 in diameter. When fully formed the clear outer ring, 
zona radiata, is 4 # in breadth, and exhibits a distinct radial 
striation. The clear vesicular nucleus measures 5 » to 8», and 
the contained refringent spherule 2°5 » in diameter. 
That the parovaria should have been so constantly con- 
founded with true glue glands—which, when they exist, are 
totally unlike them both in structure and position—is not a 
little remarkable, especially as Malpighi [148] described and 
figured both these and the true glue glands in Bombyx mori ; 
and Herold [140] figured both in Pieris brassice. He termed 
the single parovarium of this insect ‘ Das einhornige Absonde- 
rungs-Organ,’ and says: ‘ Malpighi has described and figured 
this secreting organ in the silk-moth. He thought that it 
pours a fluid into the common oviduct. This cannot be denied, 
but future observations must decide its import in the sexual 
process.’ 
Such observations were not, however, attempted, and the 
gland in question received no further attention until I made a 
series of observations upon it, which have already been 
published [833]. 
The parovaria have been observed in all, or in almost all, 
groups of insects. Stein figured the large parovaria of Hydro- 
bius fuscipes, and in this insect they are obviously part of the 
ovaries; and Gerstacker [829] says ‘the colleterial glands ’— 
alluding to the parovaria—‘are so like the ovaries in many 
Insects, that it is only possible to distinguish them by the 
nature of their contents.’ 
Jackson [851] apparently regards the parovaria of Vanessa 
as spermatheca, but as he only describes and gives figures of 
them in the pupa, I am by no means sure that the structures 
he so names are the parovaria. True glue glands—colleterial 
glands—do not exist in the Blow-fly, but they attain a large 
size in many Lepidoptera, and open into the oviduct close to 
the vulva. In these insects the parovaria and glue glands 
co-exist, and cannot be mistaken for each other. 
I had hoped to have made a series of observations on the 
parovaria of various insects, but up to the present I have been 
