244 OILMAN A. DREW. 



It occurred to me, while engaged in drawing this margin, that 

 possibly it could be photographed on a paper of a quality that 

 would allow pen drawing and thus save redrawing it. After some 

 trials a platinum paper was found that met the requirements but 

 I was surprised to find how much blacker Higgins ink was than 

 the blackest print I could make. 



Evidently, however, any mark that would take at all in mak- 

 ing a zinc etching would print the same color as the rest when 

 being put through the press, so one of the poorest of these photo- 

 graphs was finished with Higgins ink and sent away to have a 

 zinc etching made from it. The result was perfectly satisfactory. 

 It will be seen that the margins on Figs, i, 2, 3, 4, 6, 1 1, and 12 

 are all alike. The margin of Fig. I is the only one that was 

 made with pen and ink. Fig. 1 1 is a print of a negative made 

 from this margin before the rest of the animal was drawn. 

 Taking a print similar to that shown in Fig. 1 1, with pen and ink 

 there was drawn into it the organs shown in Fig. 12. Fig. 2, 

 before the alimentary canal was added, was the figure from which 

 the photograph resulting in Fig. 12 was taken. The margin of 

 Fig. 12 is then a photograph of a photograph of an ink drawing. 

 The original of Fig. 12 was then worked on to form Fig. 2 just 

 as the original of Fig. 1 1 was worked into Fig. I. Figs. 3, 4 and 

 6 are all worked onto prints similar to that shown in Fig. 12. In 

 the original paper in which these figures were published a num- 

 ber of others were based on photographs in a similar way. The 

 saving of time in the paper probably amounted to more than one 

 half, and certainly may be of importance to others. I have no 

 doubt that photographs may also be made the basis of brush 

 work, but great care will be necessary in such cases in getting 

 the proper printing value. While the figures accompanying this 

 paper show no evidence that the photograph and the ink had 

 different printing valves, they would have been very unsatisfactory 

 had they been reproduced by some other processes. 



SUMMARY. 



Circulatory System. The large size of the animal makes it 

 possible to inject the vascular system successfully. Blood from 

 the mantle is returned immediately to the heart. Most of the 



