1905.] NATURAL SCIENCES OF PHILADELPHIA. 133 



which are probably hair cells. In the early pupa these cells are large 

 and have two, or sometimes three, nuclei, but when a third nucleus is 

 present it is considerably smaller than the two more distally placed 

 ones. In the early stages this polynucleated cell contains an intra- 

 cellular duct which opens into the tubular hair, and through this duct 

 passes the secretion products of the cell for the formation of the hair. 

 The hair proper is tubular and in material stained in iron hsematoxylin 

 darker lines appear in the walls, and these structures extend for a short 

 distance down into the cell proper around the duct. The duct has 

 well-marked boundaries, docs not branch, and generally coils around 

 the second nucleus (text fig. 4). 



As the lens increases in thickness the hairs elongate by the secretion 

 of the hair cells, and as this goes on the cytoplasm of the cell is used 

 up, until finally, in the adult eye, the cell has about one-sixth the 

 volume it had in the early pupal eye. In the intracellular duct and 

 in the hair duct the products of secretion may be observed in fixed 

 material as darker bodies of irregular shape. 



These hairs and hair cells have no nerve connection, as far as I can 

 observe, and are therefore not sensoiy hairs. Just why the entire eye 

 should be covered by hairs is hard to explain, for they must undoubted- 

 ly obscure vision, and since such a hindrance is present we should 

 expect to find it compensated for by some sensory function on the part 

 of the hair. I can find no indication that such is the case. It is worthy 

 of note that the older bees have lost most of the hairs both on the eyes 

 and on the body by the time they need the eyes for prolonged flight. 

 The younger bees, up to nearly three weeks of age, leave the hive but 

 rarely, and then for short distances only, but the older bees which take 

 long journeys have the eyes much more bare. It is also noticeable 

 that all the bees, but especially the drones, brush the hairs so that they 

 all point down toward the mouth just before leaving the hive entrance. 

 No doubt, in the hive, the head, which is so frequently put into the 

 cells, becomes soiled with honey and pollen, and this action of brushing 

 may be merely to remove dirt: but, on the other hand, the arranging 

 of the partly transparent hairs in one direction may produce certain 

 results of refraction which are favorable. 



In Vanessa, Johansen describes hair cells as running the length of 

 the ommatidia without an intracellular duct and with but one nucleus. 

 He is able to locate these cells at an earlier stage than has been pbssible 

 for the bee on account of the proximal position of the nucleus. From 

 the figure of a cross-section of the cornea it would appear that these 

 cells are not so abundant as in Apis. Patten figures hair cells .for 



