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(Tbc Development of tbe C^a&pole, 



By J. W. Gatehouse, F.I.C. 

 Part VI. Plates XI and XII. 



AS in human affairs it is proverbially unsafe to predict what 

 may occur on the morrow, so I find, on referring to the 

 last article, it would have been much safer not to have 

 hazarded an opinion on the possibilities of development in 

 tadpole life which might occur in the same limited period. There 

 it was suggested as improbable that teeth could possibly be 

 elaborated, and grow from positive nothingness into a condition 

 fit for use within two days, and although the event has not 

 absolutely falsified the prediction yet, so rapidly were tadpole 

 teeth developed that, whereas on March 30th there was no sign 

 of a tooth either within or without the mouth cavity, yet on April 

 5 th numerous papillae — dark, triangular, and pointed — were 

 standing up in many ranks, only requiring to be hardened in 

 order to become useful in feeding. Indeed, it would be difficult 

 to conceive a more wonderful series of changes to occur in the 

 development of an animal whose life-history is by no means an 

 ephemeral one than actually took place in the growth of these 

 creatures between March 29th and April 7th. 



At the former date the mouth was a simple tube terminating 

 in a blind sac, although perforating the body as far as the region 

 of the heart and lungs, there being no direct connection between 

 it and the proctodeum through an alimentary canal. At the 

 later date (April 7th) the alimentary canal extended from mouth 

 to tail, consisting of a perfectly perforated tube, armed at the 

 mouth with a by no means despicable means of seizing and 

 tearing food. 



It is the object of the present paper to attempt a description 

 of some of the changes by which so profound an alteration was 

 brought about. Referring back to the diagrams accompanying 

 Parts 3 and 4 of this article (July and October, 1888), it will be 

 noticed that the greater part of the posterior portion of the body 

 is still filled with undifferentiated yelk-mass. The alimentary 

 canal may thus be seen to consist of three distinct portions — 



