1883.J On the Infectivity of the Blood and other Fluids. 449 



series, specialised correlatively with the expanded rudiment of the 

 first cleft, now enlarged into a cavam tympani, with a large 

 "Eustachian" opening. The little mandibles of the Tadpole, which 

 served as arms to carry the divided suctorial disk, and lay across the 

 fore face, become very long, and are often hinged on to their pier 

 behind the occiput, and the cartilages of the suctorial disk 

 straighten out and add to the length of the lower jaw in front. 

 These things show how this temporary " Petromyzoid," the Tadpole, 

 blossoms out into unthought-of specialisations, and becomes a quasi- 

 reptile, worthy of a place far above the Lamprey, and even far above 

 all other Ichthyopsida. 



The Myxinoids never gain the level (or platform) of the adult 

 Lamprey or the larval Frog ; they acquire no rudiments of vertebrae 

 — only a huge notochord — uniform or non-segmented. But then their 

 Ungual teeth, rudimentary in the Lamprey, and not present in the 

 Tadpole, are very large, and have a large buccal skeleton of their 

 own. They have no extra-branchial basket-work, but do develop at 

 least four visceral arches, the hyoid (or second) being very large and 

 perfect, but not segmented as in higher fishes. Everything is in a 

 generalised state. But the first arch has no lower jaw developed on it, 

 its lower part is arrested, and the two or three proper gill-arches are 

 dissociated from the gill-pouches, which are carried far back, under 

 the spine. I must refer to the main paper (Parts I and II) for details, 

 but I feel sure that every morphologist will agree with me when I 

 assert that these three related, but widely separated groups — the 

 Myxinoids, Petromyzoids, and Anura, are worthy of all the attention 

 that anatomists have given to them, and that if ever we come to see 

 how the Vertebrata have arisen, during time, from chordate forms 

 on a lower platform, we shall have to question and cross-question these 

 Marsipobranchs — not once nor twice, but many times. 



For myself, I shall be grateful if this limited contribution to the 

 anatomy of the Marsipobranch fishes should draw the attention of 

 other workers, and attract them to this fruitful field of research. 



III. " On the Infectivity of the Blood and other Fluids in some 

 Forms of Septic Disease, and the reputed occurrence therein 

 of an Increase of Virulence in Successive Inoculations." 

 By G. F. Dowde swell, M.A. (Cantab.), F.L.S., F.C.S., &c. 

 Communicated by Dr. M. Foster, Sec. U.S. Received 

 January 15, 1883. 



The remarkable fact that in some cases the blood of an animal, 

 intoxicated with putrid matter, becomes itself "infective," capable of 



