168 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



Kroyer also, in 1842 (110), described with drawings the first larva of the lobster. 

 In the following year the paper of Erdl was published on the development of the egg of 

 the lobster (62), in which some good colored drawings of the older embryos are given. 



About thirty years later, in 1874, the first circumstantial account of the meta- 

 morphosis of the European lobster was published by Professor Sars (175). His studies, 

 however, included only the first three larval stages, and, as he remarked, the changes 

 which these early larva 3 undergo, before they reach the adult state, were still unknown. 

 Some comparisons are drawn in this paper between the first larvae of the European 

 and American species. (For figures of Homarus americanus, see 175, Tab. I, figs. 18-20.) 



The first description of the metamorphosis of the American lobster was given by 

 Professor S. I. Smith, in 1872 (182), his fuller paper being published in the following 

 year. He described and figured the first three larval stages and what appeared to be 

 a fourth or fifth stage from specimens obtained in Vineyard Sound, Massachusetts, 

 in the summer of 1871. At that time the United States Fish Commission did not 

 possess the laboratory facilities which afterwards grew out of the labors of Professor 

 Baird, but notwithstanding these drawbacks this work is so carefully done that sub- 

 sequent studies will find little to correct, so far as they deal with the external anatomy 

 of the larva? described. Professor Smith says that between the third stage and what 

 he called an " early stage of the adult form " " there is possibly an intermediate form. 

 The changes in the whole appearance of the animal have been so much greater than 

 between the first and second or between the second and third larval stages that, 

 although the difference in size is inconsiderable, the whole change did not perhaps 

 take place in one molt." 



Professor Ryder, who published a short paper on the metamorphosis of the lobster 

 in 1886 (171), supposed that the first adult-like form of Smith was preceded by four 

 stages, but by only three ecdyses, the first molt (which occurs at the time of hatching, 

 as Sars (175) had found to take place in the European lobster) having been overlooked. 

 The fact of the case is that the lobster molts four times before reaching the stage in 

 which it resembles so strikingly the adult animal. It is still essentially a larva in 

 habit and structure and swims at the surface, although its earlier natatory organs are 

 reduced to mere rudiments (plate 23). 



Figures of the late embryos and of the first larva or its appendages have also been 

 published by Erdl (62), Couch (48), Cerbe, 1 and Faxon (67), the work of the latter con- 

 taining drawings by Stimpson and Alexander Agassiz, but it is not necessary to refer 

 to these in detail. 



METHODS OF STUDYING THE YOUNG. 



In the course of my studies on the metamorphosis of the lobster I have endeavored 

 to follow the history of individual larvae. This seems to the inexperienced a very 

 simple matter, but the task is beset with serious difficulties. We may isolate the deli- 

 cate larva from its natural enemies and place it under the most favorable conditions 

 which we can devise, when new foes immediately spring up or unexpected disasters 

 happen. The larvae which I studied were in most cases hatched at a known period by 

 the artificial methods now in use. Healthy specimens were then selected and placed, 



'The figures of Gerbc are very crude, as reproduced by Blanchard (19) and Duncan. They are 

 intended to represent the embryo shortly before hatching, the young immediately after hatching, ard 

 after the second molt. The original paper of Gerbe I have not seen. 



