B. From hydra-like young arising from eggs (Aurelh 

 Cyanea) and presenting the following phases of growth : — 



1. Egg. 



2. Morula ( ?) 



3. Planula (Gastrula). 



4. Scyphistoma. 



5. Strobila. 

 ■ G. Ephyra. 



7. Aurelia (adult). 



REVIEWS AND BOOK NOTICES. 



IIayden's Geologt of Colorado. 1 — Within this bulky volume 

 of over seven hundred pages is contained a mass of geological, 

 topographical and biological facts concerning Colorado, which 

 it must be confessed reflect great credit on the management of 

 the survey and the industry of the gentlemen employed upon it. 

 Large appropriations have been made by the government for the 

 survey, as accurate and timely information was wanted. We do 

 not see but that ample and speedy returns have been made. The 

 best possible topographical work was wanted, and the public have 

 it from the best possible source. Information concerning the 

 mines of Colorado is here given, while the bulk of the volume is 

 taken up with the legitimate kind of work to be expected from 

 such a survey. To this are to be added reports on the fossil ani- 

 mals and plants, and the living animals and plants of Colorado, 

 thus making it a handbook for the general reader and traveller as 



The geological and palaeontological work (fossil plants as well 

 as animals)) and- the living animals, are more fully illustrated than 

 in former reports. The outline illustrations, showing the topog- 

 raphy in combination! with the geology, are admirable. We have 



