236 EVENINGS AT THE MICROSCOPE. 



are some other points in its structure which are worth 

 noticing. In the central line of the body, just above the 

 mouth, as you see the animal in a dorsal view, there is a 

 square speck of a rich crimson hue, the edges of which, 

 when we view it under reflected light, glitter and sparkle 

 like a precious stone. But when we obtain a perfectly 

 lateral view, we perceive that the situation of this gem-like 

 speck is considerably nearer the dorsal side of the shell 

 than the mouth, and that it forms a wart-shaped pro- 

 minence on a large turbid mass which occupies the whole 

 front portion of the animal. By comparison of this organ 

 with the corresponding parts in other genera, there is 

 every reason to infer that this turbid mass is an enormous 

 brain, the nervous matter being in a very diffuse condition ; 

 and that the ruby seated on it is an eye, consisting of a 

 crystalline lens, and a layer of crimson pigment beneath 

 it. 



The oval bodies that you see attached to the hinder 

 part of the shell are eggs. Most of the females that we 

 meet with carry one or more, sometimes to the number of 

 six or seven. The specimen we are examining had two at 

 first, one on each side the foot-orifice ; but just now a 

 a third was excluded, an operation which occupied but an 

 instant, and this took its place beside the former two, so 

 that we now see three. These eggs are generally car- 

 ried by the parent until the young are hatched. The 

 oldest of these three is nearly ready for hatching, and 

 if you watch awhile you will see the birth of the young. 

 At the first exclusion, the egg, which was seen some time 

 before in the ovary, as a semi- opaque mass, of well-defined 

 but irregular shape, immediately assumes a form perfectly 

 elliptical, and its coat hardens into a brittle shell. This 

 is so transparent that the whole process of maturation can 

 be watched within the shell. The yelk is at first a turbid 

 mass, in which are many minute oil-globules. Soon it 

 divides into two masses, then into four, then into eight, 



