THE HINDGUT 207 



anal gut. It represents the enteric portion of the temporary neurenteric 

 canal connecting the posterior ends of the neurocoel and archenteron. 

 It has no derivative in the adult, but has homologues in the develop- 

 ment of most of the vertebrates. 



That portion of the hindgut between the rectum and the anus 

 forms an ectodermally lined chamber known as the cloaca. Into this 

 chamber empty the paired urogenital ducts, to be developed later. 

 Before metamorphosis there appears a ventral evagination of the 

 cloaca which gives rise to the bladder. This ultimately bi-lobed and 

 elastic organ has no direct connection with the excretory ducts as do 

 the bladders of higher forms. However, it is considered to be a reser- 

 voir, by way of the cloaca, for excretory fluids. In the closely related 

 toads, which live in hot sand, it also may be a reservoir for water 

 storage and an aid in respiration. 



