traces of any hæmatozoa-like objects can be detected at all, so that it must be inferred either that they have succumbed to the digestive action of the insect’s stomach or been disposed of along with the excreta.” An important _addendum_ by Lewis records a fortunate incident as follows:--“It was observed that nearly all the mosquitoes captured in one of the servants’ houses contained hæmatozoa, so that the supply of suitable insects in all the stages of their growth became amply sufficient for all requirements. The result of the examinations under these favorable conditions has shown that although the stomach digests a great number of the ingested hæmatozoa, as mentioned above, nevertheless others actually perforate the walls of the insect’s stomach, pass out, and then undergo developmental stages in its thoracic and abdominal tissues.” I may here observe that Sonsino has instituted a comparison between the embryos of this Filaria and those of Anchylostoma, by which it appears that the former measure 0·218 to 0·330 mm. in length, and those of Anchylostoma 0·430 mm. The hæmatozoa are about forty times longer than broad, and the larval anchylostomes only fourteen times longer. The tail of _Filaria_ is conspicuously longer. In the ‘Lancet’ for June 22nd, 1878, an announcement appeared from the pen of Mr D. H. Gabb, of Hastings, stating that a patient under his care formed the habitat of _Filaria sanguinis hominis_; and in the autumn of the same year a paper which I read to the Linnean Society in the spring was published. In that paper the following summary was offered: 1. _Filaria Bancrofti_ is the sexually-mature state of certain microscopic worms hitherto obtained either directly or indirectly from human blood. 2. The minute hæmatozoa in question--hitherto described as Wucherer’s Filariæ, _Filaria sanguinis hominis_, _Trichina cystica_, _Filariose dermathemaca_, and so forth--are frequently associated with the presence of certain more or less well-marked diseases of warm climates. 3. The diseases referred to include chyluria, intertropical endemic hæmaturia, varix, elephantiasis, lymph scrotum, and lymphoid affections generally, a growth called _helminthoma elastica_, a cutaneous disorder called craw-craw, and also leprosy. 4. It is extremely probable that a large proportion, or at least that certain varieties of these affections are due to morbid changes exclusively resulting from the presence of _Filaria Bancrofti_ or its progeny within the human body. 5. It is certain that the microscopic hæmatozoa may be readily transferred to the stomach of blood-sucking insects, and it has been further demonstrated that the digestive organs of the mosquito form a suitable territory for the further growth and metamorphosis of the larval Filariæ.