696 WILLIAM PATTEN. 



nation, however, it will readily be seen that this supposition is 

 incorrect. A number of tests have been made in order to 

 ascertain the nature of these bodies, and the results show that 

 they are some salts of uric acid. That they are not of a fatty 

 nature is indicated by the fact that treatment of the embryos 

 with hot benzole, chloroform, or clove oil has not the slightest 

 effect upon the bodies in question. Further examination with 

 a highly magnifying power shows that they consist of small 

 spheres of an extremely refractive substance, from the centre of 

 which dark lines radiate in an irregular manner, producing the 

 same appearance seen in the crystals of urea from the Mal- 

 pighian vessels. It was this similarity which first suggested 

 the true nature of these bodies, and further tests confirmed this 

 view, for after heating an embryo with nitric acid upon a glass 

 slide, and then adding a little ammonia, the characteristic red 

 colour of Murexid was formed. A still further test was used 

 by dissolving the granules in dilute caustic potash, and then 

 precipitating the urea by adding acetic acid, although this 

 method did not give such definite results as the first. 



A rather striking variation was found in the first and second 

 maxillae of Blatta, which were formed respectively of two and 

 three branches, the second maxillse thus attaining the typical 

 trichotomous structure of the Crustacean appendages. 



At first a number of abdominal appendages are developed, 

 which, however, quickly disappear again with the exception of 

 the first pair, which further develops into pear-shaped structures 

 attached to the abdomen by a stem that increases in length and 

 finally changes into a very fine duct leading into a small cavity 

 in the expanded distal extremity, which owes its size to the 

 development of extremely high ectoderm cells. No mesoderm 

 enters into the construction of this peculiar organ, which in the 

 later stages of development disappears entirely. This organ is 

 undoubtedly a special development of the first abdominal ap- 

 pendages, yet its function is extremely problematical. Rathke 

 observed what is very likely a similar organ in the embryos of 

 Gryllotalpa and which he regarded as a rudimentary gill, but 

 the remarkably thick ectodermic walls of this structure makes 



