THE AMERICAN LOBSTER. 191 



under the usual conditions. The fourth stage was reached when the larva was !) to 11 

 days old, the average age under normal conditions being about L3 days. The only 

 fifth larva reared was from 33 to 34 days old, which is nearly twice the age of this 

 larva living under the usual temperature conditions. If the larva} had been less 

 crowded in the early part of the experiment, and if the temperature of the water 

 had been raised very gradually, without fluctuations, it is possible that the results 

 might have beeu more favorable than they proved to be under the circumstances. 

 This would require considerable care and close watching, but the experiment, as 

 performed, seems to demonstrate the impracticability of making such attempts. 



The development of the embryo can be hastened by artificially raising the tem- 

 perature, but it is not certain that any advantage would attend the practice. Bumpus 

 suggests (30) that if the young were hatched by artificially raising the temperature 

 of the water during the cold months of the year, aud were then liberated into the 

 ocean, they would be certain to escape the attacks of many summer enemies. This is 

 undoubtedly true, but it is almost equally certain that the young lobsters would 

 encounter new enemies in winter and that indiscriminate destruction, which must be 

 very great at any time, would then be enhanced. 



THE DEVELOPMENT AND MORPHOLOGY OF THE BODY AND APPENDAGES. 



It was my original intention to trace in detail the development of the form of the 

 body and its appendages, but I have not been able to devote as much time as I had 

 wished to this subject. With this in view, however, I have given a pictorial history 

 of the development of the most important parts, which will be fouud chiefly on plates 

 27-35. 



Professor Smith has already described the tegumentary appendages of the first 

 three larva' and the "early stages of the adult form," which, as I have shown, compre- 

 hend the fourth, fifth, and in some cases the sixth stages. In describing these I shall 

 avoid repetition as far as possible, and pay most attention to those parts upon which 

 few or no observations have been made. 



THE BODY. 



The carapace. — The carapace arises in the embryo as folds of the ectoderm, the 

 lateral and posterior parts being the first to appear (cut 34 and fig. 234). In the first 

 larva it has the form shown in fig. 110, plate 35. It is somewhat gibbous behind, and 

 is armed in front with three downwardly directed processes, a median, slender, sharp- 

 pointed rostrum, and two lateral teeth. There is also a keel-like process on the middle 

 line near the base of the rostrum. The latter is nearly as long as the rest of the 

 carapace. The position of the future cervical fold or groove is very faintly marked. 

 In the second and third larval stages the rostrum becomes expanded horizontally into 

 a thin plate with toothed margins, but increases very little in length (figs. 109, 111, 

 112). 



In the fourth larva (figs. 113, 115, plate 35) the cervical groove is well developed; 

 the rostrum is a thin, triangular plate, bordered with spines and plumose seta?. The 

 terminal spine is usually bifid at its apex, carinate below, and turned slightly upward. 

 The length of the rostrum is now but little more than one-third that of the entire cara- 

 pace. The anterior lateral spines are much reduced. Tendon marks now make their 

 appearance, but are more pronounced in the fifth and sixth stages (fig. 114). Areas of 

 absorption, corresponding to the median longitudinal stripe, the "welt" and lateral 



