42 The Microscope. 



tween his preparations and those of his neighbors ; notes are 

 also compared ; disputes arise and the professor is appealed to 

 for a decision. In this manner, I have sometimes seen that 

 three or four preparations were studied in a single seance, last- 

 ing about two hours. 



At the end of each lesson the professor devotes a few minutes 

 toward the summarizing of the work, and a synthesis is given 

 embodying all that was observed during the lesson. 



I have seen as many as one hundred and twenty students at 

 work in the laboratory, and naturally concluded that to control 

 and direct every worker must cause great fatigue to the professor. 

 This he does not deny. " But then," he says, " the reward is great, 

 and this strengthens me more and more in my resolution never 

 to give a lesson in Cytology outside of the microscopical labor- 

 atory. " 



Now let us apply this programme and by an example show 

 how the biology of a simple monocellular living being is acquired. 

 Take for example Nodiluca, thai charming phosphorescent Infu- 

 sorium of the ocean. 



What in this minute animal at first strikes the observer's eye 

 is no doubt its beautiful peach-like form with the deep groove 

 on one side. Focussing the instrument carefully on this 

 groove he discovers an oral opening the mouth near which arises 

 the tentacle or flagellum. This is a sort of a flattened cylinder, 

 sometimes undulate or even recurved. 



Evidently the student is now studying the general morpho- 

 logy of the cell ; and examining the form of every part of the 

 animal he studies the special morphology. Who knows but that 

 the student now asks himself whether this has always been the 

 form of the Noctilnca ; and immediately he searches for the em- 

 bryonic forms of the animal, in order to solve his doubt. Prob- 

 ably he wants to know how the mouth and tentacle are formed ; 

 and finally he may place the animal into another medium, as 

 fresh water, to see what changes it will undergo. All this time 

 he has evidently studied the complete morphology of the little 

 creature. But by this time the student's curiosity is aroused 

 and he is not satisfied with such a superficial examination. 

 With the hand on the fine adjustment screw he with his eye 

 penetrates the interior of this living pearl and endeavors to de- 

 cipher the characters of its organization. Having observed the 



