Bacillus alvei. By Messrs. F. Cheshire & Watson Cheijne. 583 



shrunken by evaporation, lies on the lower side of the cell, increasing 

 in depth of tone, until in a few days nothing more than a nearly- 

 black scale remains. Should the larvae, however, escape contamina- 

 tion until near the period of pupahood, they are sealed over in the 

 normal way by a cover made of pollen-grains and wax, plate X. 



Fig. 134. 





fig. 4 a, and which is pervious to air. The cover furnishes a screen, 

 on which part of the cocoon is soon after spread, but the inhabitant 

 of the cell is marked out for death, and before very long the capping 

 or eealing sinks and becomes concave, and in it punctures of an 

 irregular character appear, fig, 4 b and fig. 134, and this is a nearly 

 conclusive sign of the diseased condition of the colony. The sense 

 of smell is also appealed to, as a pecuhar very ofi'ensive and extremely 

 characteristic odour now escapes from the diseased combs. The 

 bees in addition lose energy, but become unusually active in 

 ventilating their hive by standing at the door, heads towards home, 

 and flapping their wings persistently so that a strong out-current, 

 and as a necessary consequence, a corresponding indraught, are set 

 up. Should any attempt be made at removing a dead larva which 

 has assumed a deep brown tint, its body tenaciously adhering to 

 the cell-wall will stretch out into long and thin strings like half 

 dried glue. The microscopist can easily explain this. The thin 

 chitinous aerating sacs and trachea; do not undergo decomposition 

 at all easily, and these remaining, occasion the peculiarity referred 

 to. These tracheae are well shown in fig. 1. I'he disease is terribly 

 infectious, and once started, soon spreads from cell to cell and not 

 unfrequently from stock to stock. 



Should a speck of this tenacious coffee-coloured matter be 

 examined by a 1/4 in., it would be found to contain countless 



2 Q 2 



