372 MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES, 



this means I was able to observe the peculiar movements of the wandering cells and the formation of 

 germ-layers, which are ofteu very difficult to interpret, when we rely upon material taken by chance. 



Experience with the use of Perenyi's fluid in preparing the eggs led me to discard this reagent 

 altogether, and to substitute for it Kleiueuberg's picro-sulphuric acid, made np either with water 

 or 30 per cent alcohol. The alcoholic solution works equally well and economizes time. The Pe- 

 reuyi is too violent and uneven in its action. While it serves fairly well in some cases, it generally 

 swells out the membranes or shell by the rapid eudosmosis, and distorts some part of the egg or 

 embryo in consequence. The egg is frequently deformed and the shell ruptured. The ova should 

 be transferred directly from the killing fluid to 70 per cent alcohol, and they will then generally 

 retain their normal shape, and can thence be removed to alcohol of a higher grade for permanent 

 keeping. If, however, they are carried from the Kleineiiberg fluid to a weaker alcohol (30 per 

 cent), distortion is sure to follow, the capsule bursting and the egg sometimes exploding. 



Preparations of the entire embryo as well as sections were made, but very little was attempted 

 with the living egg. For surface preparations the hardened ova. were first punctured to allow 

 the fluid to penetrate the shell more easily and they were then stained entire, in Kleiuenberg's 

 hu'inotoxylon. They were afterwards shelled, when this was possible ; saturated with paraffin by 

 the turpentine-paraffin method, and were then mounted. While the paraffin was congealing they 

 were carefully placed in position with a hand lens. This last important and often troublesome 

 process was rendered easy by the differential property of the stain, which affects only the embry- 

 onic cells, leaving the ylok, which in preserved eggs is of a light straw color, unaltered. The 

 embryonic tissues are thus made to appear nearly black on a light background. The embryo was 

 then cut away from the rest of the egg by the microtome razor; attached to the slide by collodion 

 and mounted in balsam; or the egg was cut in two and both halves were similarly treated. All 

 drawings which represent surface views excepting Fig. 10 were made from objects thus prepared. 



In general, Kleinenberg's hiemotoxylou proved to be the best staining fluid, and it is especially 

 useful in this case, where the massive yolk contains numerous elements, the relations of which it is 

 important to determine. The carmines are less serviceable, since the food yolk is also affected by 

 them. Soda carmines (Beccari's formula) proves to be incapable of removing pigment from the 

 eyes, although it is specially recommended for this purpose. This may be easily effected by soak- 

 ing the entire tissues in very weak solutions of nitric acid for a considerable length of time. Gaule's 

 quadruple stain of ha-inotoxylon, eosiu, satl'ranin, and nigrosin was also tried with excellent results, 

 but this method is very laborious, and since our inquiries do not extend in most cases, to cell 

 structure it is unneccessary.* 



Perenyi's fluid is sometimes available for swelling the chorion and thus aiding in its removal, 

 although the embryo is liable to injury. It is also helpful in studying the egg with low powers. 

 The food yolk, which is often dark green, is affected less actively by this reagent than the embry- 

 onic tissue. The latter is turned to a waxy whiteness and is thus clearly defined for a short time, 

 but the yolk is soon decolorized unless the eggs are transferred to water, becoming pink, and liutilly 

 light yellow after preservation iu alcohol. 



PART FIRST. 

 I. THE HABITS AND COLOR VARIATION OF AiPHEUS. 



Some facts of general interest have been gathered from a study of the Alpheus iu its natural 

 environment on the coral shores and reefs of the Bahamas, and iu giving these we will limit our- 

 selves mainly to the three species which have contributed the material for the history of the em- 

 bryo, viz: Alpha/* niiiniH Say, from Beaufort, N. C., A. ht'tcrocltelis Say, from Beaufort, N. C., 

 and Nassau, New Providence, and ^4. sanlcyi, from Nassau, New Providence. The genus 

 Alpheus comprises numerous species spread over a large part of the globe, many of which are 

 closely connected by intermediate forms. From North America upwards of twenty species of 

 Alpheus have been described; five are known to inhabit the eastern coast of the United States, 

 three from Florida, and two others (A. minus and A. hcterochelis), which range from Panama to as 



* In studying the development of the lobster, which has also a largo egg, I have found it necessary to adopt new 

 methods, especially iu the treatment of the eggs for surface preparations. Iu most cases the egg-membranes are best 

 removed by the aid of hot water. 



