THE OYSTER-INDUSTRY. 239 



These, when fouud in the intestine, have usually had their living contents dissolved ont by the action of the diffestive 

 juices of the stomach. I have found in our own species of oyster, the shells of three dilfereut genera of diatoms, 

 viz, Campylodiscits, Coscinodiscus, aiul Xaricula. The first is a singularly bent form; the second is discoidal ; and 

 the last boat-sha]ied, and all are beautifully marked. Of these three types, I saw a number of species, especially 

 of the latter, but as I was not an authority u])on the systematic history of any of them, I had to neglect the 

 determination of the species. I^o doubt many more forms are taken as food by the oyster, since I saw other forms 

 in which the living matter inside the silicious cases was brown, the same as in most of the preceding forms, which 

 [ have indicated. Some of these brown forms were so plentiful as to color a considerable surface whereon they 

 grew of the same tint as themselves. But in no instance have I found any indications of the aniaial of the oyster 

 becoming colored by feeding on these diatoms, as it is said the European oyster does when feeding on Navicula 

 ostrearia, which is green, imparting its own green color to the fluids, and thus to the tissues of such oysters as may be 

 so situated as to readily feed upon it. A recent writer* gives an account of some experiments made by JNI. Puysegur, 

 of sissable in artificially producing this green color, from which I quote: "In each plate [filled with water charged 

 ■with green diatoms], according to its size, we put three to six perfectly white oysters which had never been in the 

 'dears', and the shells of which had been pi'eviously washed and brushed clean. In similar plates, like numbers 

 of the same oysters were laid in ordinary sea-water. Twenty-six hours after the commencement of the experiment 

 the oysters in the water charged with diatoms had all acquired a marked greenish hue; the other oysters remained 

 unaltered. * • * Alter the oyster had turned green it was laid in ordinary sea-water for a few days, when the 

 greenness disappeared altogether. It rea])i)eared when the oyster was replaced in fresh water containing Nackula 

 ostrearia." M. Decaisne, of the Jardin des Plaiifes, Paris, repeated the experiments with the same results. 



''Beside the diatoms, the spores of alga?, the larvie or young of many animals, such as si)onges, bryozoa, hydroids, 

 worms, mollusks, many^ of which are small enough to be taken in by the oyster, though their bodies in most cases 

 being soft and without a skeleton, it is impossible to find any traces, either in the stomach or intestine, of their 

 remains, to indicate that they have formed a part of the bill of fare of the animal. What, howevei-, demonstrates 

 that such small larval organisms do help to feed the oyster, is the fact Ihat at the heads of the small inlets or creeks 

 along the Chesapeake, where the water is but little affected by the tides and is somewhat brackish and inclined to 

 be stagnant, there always appears to be a relatively greater development of a somewhat characteristic surface or 

 shallow water fauna of minute forms. 



"In St. Jerome creek the microscopic fauna of its headwaters is entirely different from that of the body of the 

 creek ; two minute forms inhabit in vast numbers the former, while 1 sought in vain for them in the more open and 

 changeable waters of the main body of the inlet, which are brought into active movement twice a day by the 

 action of the tides. One of these forms, an infusorian,t one-twenty-fifth of an inch in length, was found covering 

 every available surface of attachment, so that countless multitudes of the naked young would be swimming about 

 in the water previous to building the curious spiral tubes which they inhabit — admirably fitted in this state as food 

 for the oyster. Beside the type referred to, there were a number of other infusoriaus, which in their so-called 

 swarming stages of development, the young would become available as oyster-food. Of such types I noticed 

 four dift'erent species, either belonging or very nearly related to the genus Cothurnia ; all of the forms built tubes 

 for themselves. I also noticed several forms of bell animalcules, the swarmers of which would become available 

 as food for the oysters lying in the vicinity. 



" The diatoms did not seem to me to be more abundant in the headwaters than in the open creek. There was 

 one moss animal of remarkable character, which 1 found in the headwaters only. This creature was very abundant, 

 and no doubt its embryos, like those of the infusoria referred to, were available as food. 



"Of free-swimming iufusorians, I noticed a number of genera; one especially attracted my attention from its 

 snake like appearance and singularly rapid contortions; it had a tuft of vibrating hairs or cilia at the heatl end in 

 close relation with the mouth. Another more abundant type was the curious genus Euplotes, with a thick shell 

 inclosing the soft protoplasm of the body; the latter was of an oval form, flat beneath and rounded on the back, 

 so that the resemblance, when the lai'ge foot like cilia were in motion, carrying the animal about, was strikingly like 

 a very minute tortoise, the resemblance being heightened when the animal was viewed from the side. 



" Bod-like algte, of minute size, the larvea of crustaciB, especially the vast numbers of extremely small larval 

 copei)oda, must enter as a perceptible factor into the food-supply of the oyster. 



" There is no doubt but that the comparatively quiescent condition of the headwaters of these inlets and creeks, 

 available as oyster-planting grounds, are more favorable to the propagation of minute life than the oi)en bay or 

 creeks, where the temperature is lower and less constant. Practirally, this is found to be true, for oystermen seem 

 to be generally agreed that oysters "fatten" more rapidly, that is, feed more liberally in the headwaters— blind 

 extremities of the creeks — than elsewhere. This notion of the oystermen is in agreement with my own observation.s 

 during the past year. Oystermen also assert that oysters "fatten" more rapidly in shallow waters than in deep 

 ones, a point upon which I made but few observations; but such as I did make tended to confirm such an opinion. 



*Tlie Green Color of Oysters, H. M. C. In Nature, vol. xxii, pp. 549-50, IdSO. Translated from the Revue Maritime et Colouiale, 

 February, leSO. 



tOu the oerurreuce of Frehi produrin (Wright), in the Chesapeake hay.— AnurUan Xaiiiiali'il. 1880. pp. 810,811. 



