274 THE AMERICAN MONTHLY [Oct 



that the form then found was a transition of Biddul- 

 ])hiii turgida into Biddulphia Ifevis. 



The mode in which Trochiscia moniliformis grows is this. 

 At first it appears as a sphere made up of a substance 

 which we call protoplasm. It cannot be analysed chemi- 

 cally because it changes. At any rate it appears when 

 viewed by the eye as without a shell or hardened loricaj 

 as it is called, and without any nucleus or therefore any 

 nucleolus. The cell contents are called endochrorae and 

 other things. Immediately after these there appear cer- 

 tain minute dots which are of a higher refractive index 

 than the surrounding water, and are therefore differenti- 

 ated in optical character from the endochrome and proto- 

 plasm in which they are in contact. The endochrome is 

 olive colored, these dots seem to be colorless. Soon after 

 or before there appear larger dots which have been called 

 oil globules, for they seem to be oily and colorless and 

 thick in consistence. The first become seeming anthozoa 

 or male organs. The oil globules are seeming ova or fe- 

 male organs. The anthozoa fulfil their purpose by im- 

 pregnating the ova and then disappear. The ova persist. 

 And the Trochiscia has also developed a shell which is silic- 

 eous or composed of aluminum silicate. It is now a sin- 

 o-le Trochiscia but is also a single individual of Melosira 

 nummuloides, for looking at it carefully it is seen to be 

 on what is known as the side view, or when the valve is 

 exposed to view, to be a clear circle with very fine ma rkings 

 but with no umbilical portion separated from the other or 

 mar'^inal portion. When the umbilical portion appears 

 the name that it goes by is Hyalodiscus. Soon it be- 

 ii-ins to grow by adding another individual to itself, and 

 then another, and another, until a chain is formed. But 

 whilst it does so the shell is not smooth where it joins to 

 the next shell. It is flattened there and the markings are 

 indistinct. This is the umbilical portion. Now can this 

 chain be a Melosira nummuloides or a Trochiscia monili- 



