674 THE GENERATIVE ORGANS. 



30 fj, in diameter. When fully formed the clear outer ring, 

 zona radiata, is 4 p in breadth, and exhibits a distinct radial 

 striation. The clear vesicular nucleus measures 5 p to S/i, 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 brassicae. 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 [333]. 



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 [329] 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 [351] 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 

 si/c 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 

 ovaria of various insects, but up to the present I have been 



