110 Dr. Fr. Meinert on the Ugimyia-La>-i?a. 



end. The three or four cases just mentioned agree with 

 the theory of Mr. Sasaki to a certain extent. Tn some im- 

 portant points, however, the distinguished Japanese savant 

 may be mistaken, as I shall now try to prove. 



The cup or sac is not, I should say, constructed by the 

 maggot "by heaping up the fats and muscular fibres." It is 

 merely a portion of the tracheal system of the silkworm 

 swelled by the presence of the parasite and tinged brown by 

 its excrement. Having forced its way into the trachea, 

 the young maggot imbeds itself there, with its spiracle- 

 plates turned towards the stigma of the silkworm and with 

 its mouth peeping out from the trachea into the body-cavity 

 of the host. By-and-by, as the maggot grows, the trachea 

 expands and swells, its outer part assuming a brownish 

 colour from the maggot's excrement, while the inner portion 

 remains uncoloured. I therefore conclude that if a living or 

 fresh silkworm infested by a maggot is cut open for investi- 

 gation, the inner part of the trachea or sac, being thin and 

 white, may break off, while the outer, brownish, part remains 

 in connexion with the skin of the silkworm. This last-men- 

 tioned brownish part of the trachea, then, is the " cup " of Mr, 

 Sasaki. By means of the microscope it may be clearly seen 

 that the inner surface of the sac is formed exclusively by 

 the inner membrane of the trachea, the tunica intima, and 

 does not show any trace of muscular fibres or of fats. It 

 is also observable that on the tunica intima of the main 

 trachea forming the inner surface of the sac, as well as on 

 the other adjacent smaller tracheas, the brownish colour is 

 more intense, while the muscular fibres and fats sur- 

 rounding the sac are much less coloured. From the same 

 source, viz. the excrement of the maggot, the dark spot on 

 the silkworm's skin also derives its existence. That the sac 

 is formed by the trachea is proved, moreover, by the fact that 

 the mouths of the smaller tracheal are easily distinguished on 

 its inner surface. 



As to the sticking-power of the colouring-fluid (excrement 

 or saliva) , it must be very slight indeed, or, rather, none at all ; 

 otherwise the sac or cup would adhere to the skin of the 

 silkworm, and probably be thrown away, together with the 

 cast-off skin, at its transformation into a pupa. But this is 

 not the case : the sac remains inside the host, and consti- 

 tutes the dark lump found behind the stigma of the pupa. 

 With proper care this lump may be unrolled, and proved 

 to be a sac large enough to embrace the maggot living in 

 the body of the pupa. As will be remembered, the maggot 



