PUTKAM ON PULVINARIA INNUMERABILIS. 321 



The secretive organs are very numerous and highly developed. Besides 

 the so-called mulpighian vessels already mentioned, there are the salivary 

 glands, the viginal glands, and the numerous v:ax-secreting glands. To 

 these might be added the retort-shaped organs in which the buccal setae 

 are developed, but I know nothing of their particular structure except 

 by seeing the se se coiled up in them. 



The salivary glands (fig. 48,/,/') consist of two groups of six or more 

 spherical glands, Ijting one on each side of the mouth parts, with which 

 they appear to be connected, but iu just what manner I did not observe. 

 Each spherical gland appears to consist of two nucleated cells. These 

 organs have been quite fully described by Dr. Mark.* 



The vaginal glands (fig. 47,/', /') consist of two groups of three large 

 many celled glands, lying one on each side of the vagina. Each group 

 discharges its products into a large spindle-shaped vessel (g, g') which 

 becomes very narrow at its outlet. The outlets of both vessels (k) are 

 close together a very short distance above the outlet of the vagina at the 

 vulva (d). It is probable that these glands secrete a viscid substance 

 with which the eggs become coated in their passage, and which after 

 their expulsion causes the fine waxy powdery rings to adhere to the sur- 

 face, as has been observed to be the case. 



The wax secreting glands so far as I. have observed them, consist of a 

 single spherical gland for each pore (fig. 44,a). This appears to consist 

 of a single cell surrounded by small branching tubes which unite to- 

 gether at one point to form a long slender straight tube (6,c) extending 

 to the orifice (d). The outer half (c) of the tube appears to be larger 

 than |the inner half {h). The wax secreting 2iores are of three kinds: 

 The first are circular with a small central tubercle, surrounded by a 

 number of fine pores (fig. 49), these give rise to the fine powder-like sub- 

 stance which when highly magnified is seen to be in the form of rings 

 (fig. IS a). These pores are very numerous, especially on the ventral 

 surface of the abdomen, and in the spiracular grooves as above des- 

 cribed. It is possible that these may sometimes give rise to filamentary 

 substance, but I do not think this is usually the case. In the second 

 form (fig. 50) the central tubercle is enlarged and greatly prolonged 

 forming a long stout spine (/), undoubtedly pierced by numerous very 

 minute pores, through which the waxy substance issues in a soft state 

 and unites to form a long hollow filamentary tube (g). It is from these 

 waxen tubes that the so-called "cottony," "w^oolly,"or " silken" sub- 

 stance of the egg nest is formed. These spines are numerous all around 

 the margin, and a few on the underside of certain of the abdominal seg- 

 ments as above described. The third kind of pores, those on the dorsal 

 surface, I have not distinctly seen. They are probably very numerous 

 and very minute, corresponding to the sweat glands of the higher ani- 

 mals. At any rate the dorsal surface is entirely covered with a uniform 

 layer of wax very thin in the young, but increasing with age when it 

 .generally becomes cracked, but never becoming sufficiently thick to 



* Beitrage^ etc., pages 29-5], 



