i8 THOMPSON YATES LABORATORIES REPORT 
Grassi and Calandruccio 1 traced out the development of the embroyos in 
Pulex sermticeps (of the dog and cat), Pulex irritans (of man and dog), and Rbipicepbalus 
siculus, Koch (a dog-tick). They describe the following stages : — 
First Stage. Embryo found in the blood of dogs, and in the intestine and 
body cavity of fleas. Length 280 breadth 5//. Body slightly thinned in front, 
but ending bluntly : behind it tapers and ends in an almost hair-fine point. It is 
smaller than the embryo of F. immitis, and possesses the characteristic that they fix 
their oral end to the coverglass. At the front end can be made out a fine canal, 
representing the oesophagus. In those which have reached the body cavity there 
can be made out a certain trace of the intestinal tract and of the anus. The embryo 
executes snake-like movements. 
Second Stage. Found in the fat cells, seldom free in the body cavity. The 
larvae of the previous stage first shorten without thickening, then thicken and finally 
lengthen. The cells of the larvae are larger, and the organs more distinct. The 
body is cylindrical, and in front has a finger-like papilla 5-6 /x long, covered with 
cuticle somewhat thickened at the free end, and appearing as though filled with a clear 
liquid. Long pointed tail. Parts of the alimentary tract are becoming differentiated. 
The genital apparatus is just appearing. The worm has no movement. 
Third Stage. A moulting of the cuticle takes place either in the cell or when 
free in the body cavity. Length reaches 1*5 mm. The front end is blunt, the 
papilla of the previous stage disappears. Hind end has three papilla, one terminal 
dorsal, two other almost terminal, and ventral. The fine point of the tail has 
disappeared. Further development of the alimentary organs — mouth opening has 
four papillae. The worm shows active eel-like movements. 
Fourth Stage. Only once seen. The larva was encysted, and was consider- 
ably larger and thicker. Genital apparatus developed. The tail, besides the papillae, 
bears a little process (as in adult). 
Stages three and four are similar to the adult, and much further development 
cannot take place. 
Attempts, however, to infect dogs with infected fleas failed. 
Filaria irritans. Rivolta 
Syn. Dermofilaria irritans. This name is given to a nematode larva, which 
measures about 3 mm. in length ; its head is slightly marked off by a neck from 
the body ; the tail tapers and terminated in a blunt notched point. The mouth is 
round, and appears to be provided with lips. At a little distance from the head 
end an opening is seen. The anus occurs at the point where the body tapers into the 
tail. The integument bears fine transverse striations. 
The life history is unknown. These larvae are found in the 'summer sores' 
or ' granular dermatitis ' or horses and donkeys. 
1, Grassi and Calandruccio, Ccntralblatt fur Bakteriologie, 1890, vii, 18-26 
