280 LECTURES ON MOLLUSCA. 



ence. In the old days when all knowledge was supposed to be centered 

 in Lamarck, we had nothing to do but to study his system and follow 

 it. We are now turned loose on a new sea of inquir} r ; where every 

 voyager makes his own* discoveries, which is right; and his own spec- 

 ulations, which may be correct or very erroneous. 



Our uncertainties for want of knowledge are quite sufficiently dis- 

 couraging; but for these we must be prepared. With every fresh, 

 patient, and honest observation, these will be steadily lessened, in 

 spite of the prejudice and human tempers which ought not indeed to 

 be allowed to enter into the domain of science, but alas ! are to be 

 found there as rife, as in any other department where men enter on 

 each other's paths. And it ought to be an incentive to pursue this 

 branch of study that there is so much to be done ; and so much, too, 

 the materials for which are easily accessible. The principal requisites 

 to insure really useful results are not indeed great talents or special 

 acquirements, which fall to the lot of but few; but what an ordinary 

 person may possess himself of, an accurate eye, patience, and honesty. 



It is well, in the present state of science, to take nothing on trust. 

 What is copied from book to book, and what is repeated from figure 

 to figure, may be correct; "but then, on the other hand, it may not." 

 Very few can examine all things with their own eyes ; and the greatest 

 authors take many things $>n trust, which humble students may prove 

 to be unfounded. It is a mistake to suppose that the evidence of the 

 senses is infallible. The eye has to be trained to see, just as much as 

 the ear to appreciate false and true harmonies, or the hand to discrim- 

 inate weights. Very few persons at the beginning of their investiga- 

 tions see things in the microscope as they do after long study. The 

 best artist, if required to draw a shell, might very likely overlook 

 features which a student has learned to see at once. Therefore let a 

 man work some time, comparing his observations with the books, and 

 repeating them under different conditions, before he considers himself 

 competent to trust his own eyesight. 



Let the student especially avoid hasty conclusions. Because char- 

 acter A is found to be coordinate with character a in one class of 

 shells, let him not infer that it is so in another; still less that char- 

 acter B is coordinate with character b. The following table may 

 serve as a lesson of caution, to show how little can be gathered from 

 general similarity in appearance. It furnishes some of the more 

 striking examples of Grasteropods similar in' form of shell, but known 

 to belong to different families by peculiarities in the animal. 



TABLE OF SIMILAR SHELLS, BELONGING TO DIFFERENT FAMILIES OR GENERA. 



Murex, Muricidce. Cerastoma and Vitularia, Purpuridce. Kanella 

 and Triton, Tritonidce. 



Chrysodomus, Muricidce. Strombella, Buccinidce. Io, Melaniadce. 



Engina, Muricidce. Ricinula, Purpuridce. 



Anachis, Muricidce,. Nitidella, Purpuridce. Columbella, Buccinidce. 



Cominella, Muricidce. Buccinum, Buccinidce. Truncaria, ? Purpu- 

 ridce. 



Pisania, Muricidce. Iopas, Purpuridce. Peristernia, Fasciolariadce. 



