MALARIA EXPEDITION TO NIGERIA 17 
investigations, he claimed that Sonsino was led astray by the coincidence that F. 
recondita was present in the dogs he examined, the embryos of which were mistaken 
for those of F. immitis. Grassi then thought the intermediary host to be a crustacean 
or mollusc. 
However in 1900 he 1 describes the development of these embryos inside the 
mosquito. 'The embryos sucked up by Anopheles migrate into the malpighian tubes, 
where they continue their development behaving more or less like the other blooci 
filariae already known. The larvae, arrived at maximum development, abandon the 
tubes and enter the general body cavity leaving behind the old cuticle : there they 
progress towards the head and collect there rapidly in the prolongation of the 
general body cavity within the labium (called also the inferior labium), occasionally 
in the palpae.' In their experiments these authors seem to have allowed a period ot 
thirteen or fourteen days for the complete development of the embryos in Anopheles. 
They do not appear, however, as far as we have been able to ascertain to have carried 
out the infection of healthy dogs by the bites ot infected Anopheles. One experiment 
is described, undertaken on July 19, 1900, in which a healthy dog was injected 
subcutaneously with larvae, collected in a drop of normal saline solution, from the 
labium of two infected Anopheles. At the post-mortem on August 4th (a period of 
sixteen days) there was found ' in the subcutaneous tissue near the genitals, a very 
small female filaria which must be judged Filaria immitis, still immature. We were 
able to preserve only its anterior half sufficiently for diagnosis.' This does not seem 
to us very satisfactory ; details of the appearance and anatomy of this anterior half 
of an immature Filaria immitis not being given. 
Filaria recondita. Grassi - 
The female only is known. This is about 3 cm. long, 0*178 mm. broad. 
The transparent body tapers towards both ends, more especially posteriorly. The 
integument is nonstriated. The anterior extremity is obtuse, bears at least tour 
very small papillae close to the buccal orifice. Posterior extremity is also blunt, 
and has three papillae, one terminal and two lateral, and also several small papilliform 
projections. The mouth is followed by a very short cylindrical oesophagus, somewhat 
less than 2*5 mm. long. The anus is at a distance of 228 fx from the tip of the tail. 
The uterus is double, the vulva at a distance of 840^ behind the mouth. 
Life history. Up to the present only a single female specimen (which was 
immature, containing neither embryos nor eggs) has been met with. It was found 
coiled up but not encysted in the adipose tissue near the hilum of the dog's kidney. 
The embryos have been studied by Gruby and Delafond, Lewis, Manson, Grassi, 
Sonsino, and others, in France, China, India, and Italy. 
1. Grassi and Noe, British Med. Jour12.il, 1900. Nov. 3, p. 1306. 
2. In a footnote in his article on 'Filariasis' in the Encyclopaedia Medica, Vol. Ill, Nuttall says : 'Sonsino (personal 
communication, December, 1899) considers it doubtful that this is a 'good species,' the determination having been made upon 
a single female specimen,' 
