M. Leuckart on the Reproduction <>f Bark-lice. 411 



the cellular matrix. The further side of the cylinder is imper- 

 fectly shown, from having been out of focus in the photograph. 

 The secondary fasciculi, proceeding to the leaf-stalks and root- 

 lets, give the exterior a bristly appearance. 

 Fir/. 12. A diagrammatic transverse section of the caudex. The interrupted 

 circle represents the cut extremities of the fasciculi of the netted 

 cylinder, and the scattered dots on its exterior those of the 

 secondary fibro-vascular bundles of the petioles and rootlets. 



[The above figures are mostly from photographs of the original 

 specimens (now in the Museum of the Royal Botanic Garden, 

 Edinburgh) by Mr. Andrew Adams of Aberdeen.] 



XLI. — On the Reproduction of the Bark-Lice (Chernies, &c.)j 

 a farther Contribution to the Knowledge of Parthenogenesis. 

 By Rudolph Leuckart. 



[Concluded from p. 32/.] 



Before tracing these differences and analogies further, it is 

 necessary, however, that we should glance at the anatomical 

 arrangement of the generative apparatus in our Bark-lice (PI. VII. 



In the four or five species (three or, if C. Abietis is to be 

 regarded as two species, four Chermes, one Phylloxera) there is 

 a perfectly unmistakeable analogy in the formation of the female 

 parts ; and this is the more striking, as it at the same time fur- 

 nishes a perceptible distinction from the female organs of the 

 true Aphides*, which propagate both by oviparous and vivipa- 

 rous generations. On the whole, however, the type of the 

 organs in question is the same as that we meet with in the 

 latter. 



With regard to the ovaries, it must first be indicated that the 

 egg-tubes of our animals are in all cases composed of two, or 

 even three (Phylloxera) chambers (fig. 1). From the previous 

 statements with regard to the structure of the egg-tubes in the 

 ordinary Aphides, we might suppose that this is the expression 

 of a thorough-going distinction between these two groups ; but 

 I have ascertained by my investigations of this year, that among 

 the Aphides there are species with plurilocular egg-tubes, al- 

 though the greater number of them certainly have only one 

 chamber, like the Coccina. Among these species with pluri- 



* As far as we know, Chermes and Phylloxera are the only Aphides with 

 solely oviparous generations. That there are also species with only vivi- 

 parous generations, as stated by Kaltenbach, appears to me very doubtful. 

 In Schizoneura, which is said amongst others to be in this case, I have 

 proved the existence of an oviparous autumnal generation in the small 

 memoir already repeatedly mentioned. 



