August 30, 1889.] 



SCIENCE. 



145 



favor of the lambs fed on nitrogenous food, it is when we come to 

 compare the amount of gain in relation to the amount and cost of 

 the food consumed that the most striking figures are brought out. 

 Both in the amount of food consumed for one pound of gain, and 

 the cost of gain per one hundred pounds, the advantage is very 

 markedly in favor of lot IV, the lot fed on nitrogenous food. It 

 costs a little more than a cent and a half per pound, or twenty-six 

 per cent more to put a pound of gain upon the lambs that were 

 fed on corn, timothy hay, and roots than it did to put a pound of 

 gain on those that were fed wheat bran, cotton-seed meal, clover 

 hay, and roots. 



The lambs were shorn Nov. 15, or ten days before the beginning 

 of the experiment. They were shorn again the day before they 

 were slaughtered, so that the wool obtained was the growth of 

 160 days. The weight of the wool from both lambs in each lot 

 was, lot III, 4.25 pounds ; lot IV, 7.31 pounds ; lot V, 6.63 pounds ; 

 lot VI, 6.19 pounds ; — the last three lots showing an increase over 

 lot III of 73, 56, and 46 per cent respectively. This coincides with 

 the results of the experiments last year, in that nitrogenous food 

 seems to largely affect the growth of wool. It seems to show fur- 

 ther that even a small increase in the nitrogenous matter of a ration 

 has a decided influence on the growth of the wool, for lots V and 

 VI, whose ration was intermediate in character, gave very nearly 

 as much wool as lot IV. In the experiments of i888, already re- 

 ferred to, the percentage was not so great in favor of the lambs fed 

 on nitrogenous food. 



The lambs were slaughtered on April 25. The blood was care- 

 fully caught in a clean pail, and it and all the important internal 

 organs were weighed. The carcasses were hung up in a cool place 

 to stiffen for two days, and were then cut up, and the parts care- 

 fully examined. Before they were taken down, however, they were 

 weighed and most carefully inspected by the different members of 

 the staff. The most striking difference that was apparent, as the 

 carcasses hung upon the hooks, and after they were cut up, was 

 the evident leanness of the two belonging to lot IV, which had been 

 fed nitrogenous food. The kidneys were not covered, and there 

 was very little loose fat next the skin, while in all the other car- 

 casses the kidneys were more or less completely covered, and there 

 was a layer of tallow of greater or lesser thickness between the 

 skin and body. The carcasses of lot III had the most of this tal- 

 low. The same thing is shown in the amount of caul fat and kid- 

 ney fat. While an expert butcher would have undoubtedly selected 

 the carcasses of lots V and VI as furnishing the most saleable 

 mutton, the carcasses of lot IV had little or no unpalatable adipose 

 matter, and those of lot III showed much the largest percentage 

 of waste fatty matter about the root of the tail and in the flanks. 



The weight of evidence of all of the experiments at Cornell, to- 

 gether with results obtained by other experimenters in the same 

 field, seems to show : that corn, as an exclusive grain ration, does 

 not give the best results, either in amount, quality or economy of 

 production, when fed to growing or fattening animals ; that the 

 amount of water drank, especially in the case of these lambs, is a 

 pretty certain indication of the rate of gain ; and that the production 

 of wool is very greatly dependent upon the nitrogen in the ration. 



The value of the manure made from the animals fed is a matter 

 of prime importance, to all eastern farmers at least. And often the 

 manure left on the farm represents a large part, if not the whole, 

 of the profit made from feeding a lot of animals. For this reason 

 there were calculated the manurial value of the rations fed the dif- 

 ferent lots. From this it appeared that while the first cost of the 

 ration of the nitrogenous fed sheep vi^as larger than that of the car- 

 bonaceous, yet when the value of the manure [is subtracted, the 

 cost of the former is less than half of the latter. 



PEARL OYSTERS. 



The presence of nodules or tubercles on the interior surface of 

 the shells or valves of lamellibranch (bivalve) mollusks is of fre- 

 quent occurrence. These excrescences are nacreous or otherwise, 

 according to the character in this respect of the shell in which or 

 upon which they occur. They are found alike in fresh-water and 

 marine species. In the pond and river mussels they are chiefly due 

 to interior causes ; in marine forms, like the cockles, mussels, the 



scallops, etc., these formations are generally traceable to exterior 

 causes. It is often the case that specimens of the large scallop of 

 the New England coast are so burrowed into by a species of sponge 

 that nearly the entire inside surface of the valves will be roughened 

 with sharp, thickly-set pustute. In all the marine species in which 

 those nodules occur it will usually be found that the substance of 

 the shell has been bored into from the outside by either a species of 

 pholad or lithodomus. 



Neither of these forms are, properly speaking, either parasites or 

 commensals. They are, more definitely, " domiciliares," as stated 

 by Mr. Robert E. C. Stearns of the Smithsonian Institution, and 

 excavate their burrows, not for the purpose of getting at the softer 

 parts of the moUusk upon whose shell they have " squatted " in 

 order to use said softer parts as food, but solely for the purpose of 

 a residence or domicile. 



The burrows of these shell-boring pholads and lithodomi are at 

 first quite small, increasing in size in the same ratio as the bur- 

 rower increases in age or in growth. After a while the depth of 

 the boring is equal to the thickness of the shell in which it has 

 been made, and the occupant of the latter, in order to keep his own 

 shell intact and maintain the integrity of his own domicile, com- 

 mences depositing layer upon layer of nacreous or porcellaneous 

 matter, as the case may be. In keeping pace with the continued 

 encroachments of the domiciliary squatter upon the outside, 

 this deposit finally becomes a more or less conspicuous protuber- 

 ance. 



Sometimes these nodules or tubercles are due to some foreign 

 inorganic matter, a particle getting in between the mantle of the 

 mollusk and the inner surface of its shell. In such cases it is, we 

 may say, at once plastered over, and thus fixed upon the surface of 

 the valve. Free concretions, i.e., unattached or non-adherent nod- 

 ules, are, as is well understood, caused by some particle, organic 

 or inorganic, becoming in some way lodged exclusively in the soft 

 parts of the body of the mollusk, and so far away from the surface 

 of the shell as not to admit of its being cemented to it. 



No doubt many of the mollusca, both gastropod and lamelli- 

 branch, contain or are inhabited by true parasites. In certain spe- 

 cies of fresh-water mussels a species of water mite has been de- 

 tected, and sometimes thread worms and other forms occur. 



A small species of crab, an epicurean no doubt, finds a salubrious 

 habitation in the common oyster, but parasites of any considerable 

 size appear to be rather rare. Besides the species above referred 

 to, another small crab is sometimes found in the common mussel 

 and the large scallop before mentioned. It is doubtful, however, 

 whether these crabs are really parasites or only commensals, though 

 probably the former. 



There is, however, evidence of the occurrence of fishes of two 

 species as parasites in the true pearl oyster, or mother-of-pearl 

 shell, not by the presence of the living fish, or even by dead speci- 

 mens of " fish in the flesh," if we may use so convenient a paradox, 

 but by their entombed remains in the form of nacreous nodula; or 

 tubercles on the shells or valves of the said mollusk. 



At a meeting of the Zoological Society of London June i, 18S6, 

 Dr. Giinther e.xhibited a specimen of a small fish of the genus fic>-- 

 asfei- embedded in a pearl oyster, and said : " This specimen is an 

 old shell, in which there is imbedded, behind the impression of the 

 attractor muscle, a perfect individual of a fish belonging to the 

 genus fierasfer. The fish is covered by a thin layer of pearl sub- 

 stance, through which not only the general outlines of the body but 

 even the eye and the mouth can be seen. The parasitic habits of 

 fierasfer are well known. The fish, instead of introducing itself 

 into the cavity between the two halves of the mantle, penetrated 

 between the mantle and the shell, causing irritation to the moUusk. 

 which the latter resented by immediately secreting the substance 

 with which the intruder is now covered. It is remarkable to note 

 that the secretion must have taken place in a very short time, at 

 any rate before the fish could be destroyed by decomposition." 



After entering the shell, which of course must be at such time as 

 the valves are partially open or gaping, these fishes find no obstruc- 

 tion to their course as they push their way towards the interior be- 

 tween the mantle and the smooth inner surface of the valves until 

 they approach the adductor muscle, and here they find a barrier 

 which most likely causes them to expend somewhat greater ac- 



