Prof. Ehlers on the Develojmient of Syngamus trachealis. 237 



certain character to prove the presence of 8y7igamus in a 

 coughing bird (as the phenomena of coughing may be pro- 

 duced by very different maladies) is the examination of the 

 dung of the bird, because as soon as the disease has continued 

 a little longer, so that the parasites have become sexually 

 mature in the trachea, the ova may be easily found in the 

 dung. I made this observation on the above-mentioned car- 

 dinal grosbeak, and found it confirmed when I saw at M. von 

 Freyberg's, in Regensburg, a Euplectes melanogaster (Sw.) 

 which coughed a little in the evening and morning, and in 

 whose dung the readily recognizable ova of Syngamus imme- 

 diately occurred. 



I made use of the material at my disposal, in the first place, 

 to trace the development and migration of Syngamus. Ajpriori 

 it was not probable that a bird would acquire the parasite 

 when it ate the ova of a Syngamus^ since the ova occurred in 

 the dung of birds, and evidently pass through the intestines 

 uninjured when the bird swallows the mucous masses or frag- 

 ments of the worm containing ova which have been expelled 

 from the trachea. An experiment made in this direction re- 

 mained so far without result that a canary which I allowed 

 to swallow a female Syngamus filled with mature ova did not 

 acquire the parasite. 



It seemed more probable that the ova, when expelled from 

 the trachea or evacuated with the fasces, would be developed 

 at first outside the bird. Leuckart's statement * that the 

 species of the genus St)-ongyIus which are parasitic in the 

 lungs have an intermediate form, which lives in an interme- 

 diate host, belonging generally to the Insecta, together with 

 the statement of M. von Freyberg, that he had observed the 

 disease among his birds especially after they had been fed 

 with insects, induced me to give cockroaches and mealworms 

 the opportunity of eating the ova of Syngamus, and allowing 

 the latter to become developed in them. With insects thus 

 infected I thought to introduce the worm into the birds, but 

 without result. I was, however, soon put upon the track of a 

 simpler mode of development. 



The ova of Syngamus are developed, with sufficient mois- 

 ture and warmth, in the open. The matm-e ovum oi Syngamus 

 is evacuated by the female in various degrees of segmentation; 

 it occurs under these conditions in the mucus of the air- 

 passages in diseased birds, and somewhat further devclo])ed, 

 but always so that the vitellus consists of a number of globides 

 of segmentation, in their fteces. It has a cylindrical or slightly 

 ellipsoidal form, with a length of 0"11 millim. and a breadth 

 * Die menschlichen Parasiten, Bd. ii. 18G8, p. 402, 



