MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 337 



GONODACTYLUS CHIRAGRA. 



''There are few orders of animals of which we arc more ignorant than we are of the Stomato- 

 l>ods. They are well known as museum specimens, and every natural-history cabinet contains one 

 or two, which have been brought home as rare curiosities from distant seas; but we know hardly 

 anything of the habits of the living animals. They are abundant and widely distributed, but like 

 most rapacious animals they are very alert, taking alarm at the slightest disturbance and retreat- 

 ing to the depths of their burrows at the bottom of the ocean, where they are so completely hidden 

 tioui observation that their capture is difficult, and any attempt to study them in their homes is 

 almost out of the question. 



The habits of Squilla? are tolerably well known, and in my report on the Stomatopoda, collected 

 by II. M. S. Challenger, I have given an account of the habits of Lysiosquilla based upon observa- 

 tions made at Beaufort, North Carolina; but, except for a few scattered and fragmentary notes in 

 the various descriptive papers, this is the whole of our knowledge of the order. During the sea- 

 sons of 1886 and 1887 I was so fortunate as to find in the Bahama Islands Gonodactylus chiragra 

 living in localities which were peculiarly favorable for observing its habits, and I am now able to 

 supplement my report upon the Challenger collections by an account of this interesting species, of 

 which little had hitherto been known, except the fact that it is the most cosmopolitan of the 

 Macroma abounding on the shores and islands of all tropical and subtropical seas. 



I also obtained its eggs in abundance and succeeded in rearing the young from them iii 

 aquaria, and am now able to make a contribution to a subject upon which there were hitherto no 

 direct observations, for it is a noteworthy fact that while the older larvae of Stomatopoda have 

 long been known, and while many genera and species of them were carefully figured and described 

 and named by the older naturalists before their relationship to the adult Stomatopoda was sus- 

 pected, not a single species in the whole order has, so far as I am aware, been reared from the 

 egg and in this way identified with its specific adult. 



While the adults usually inhabit burrows in the bottom the larvae swim at the surface of the 

 ocean, and as none of the animals which are captured in the surface net exceed them in beauty 

 and grace, their glass-like pelagic larvae are familiar to all naturalists who have had an oppor- 

 tunity to study the surface fauna of the ocean. Their perfect transparency, which permits the 

 whole of their complicated structure to be studied in the living animal, their great size and 

 rapacity, the graceful beauty of their constant and rapid movements, can not fail to fascinate the 

 naturalist. Unfortunately they are as difficult to study as they are beautiful and interesting, and 

 notwithstanding their great abundance and variety, only two or three of them have been traced 

 to their adult form. 



Unlike most Malacostraca the Stomatopoda, instead of carrying their developing eggs about 

 with them, deposit them in their deep and inaccessible burrows under the water, where they are 

 aerated by the currents produced by the abdominal feet of their parents. The eggs quickly 

 perish when deprived of this constant current, and as it is very difficult to obtain them at all, I know 

 of no Stomatopod which has ever been reared from an egg under observation. The older larv;e 

 are hardy and are easily reared, but they are seldom found near shore, and microscopic research 

 is so difficult at sea that I know of only two cases in which they have been kept until they assumed 

 the adult form. As I have stated in my report on the Challenger Stouiatopoda, I have reared a 

 young Lysiosquilla excavatrix from an old larva which was captured at the surface, and Faxon 

 has in the same way obtained the young Squilla enipusa. The young larvae are common near 

 shore, but as they seldom survive a uioult in captivity they can not be identified in this way. 



The growth of the larvae is slow and the larval life long, and as they are as independent and 

 as much exposed to changes in their environment and to the struggle for existence as the adults 

 they have undergone secondary modifications which have no reference to the life of the adult, and 

 are therefore unrepresented in the adult organism. The larvae have been arranged in genera and 

 species, but their generic characteristics are quite different from those upon which the adult genera 

 are based, and this is true in a still greater degree of their specific characteristics. As they 

 undergo great changes during their growth different stages have been described as distinct species 

 or even genera, and it is not easy to select from the rich gatherings which are brought home by 

 S. Mis. 94 22 



