>30 



SCIENCE. 



[Vol. XI. No. 275 



idea without due credit, and partly because I am gratified tliat a 

 thoughit whicli has lain long in my mind is now confirmed by so 

 eminent a biologist and so profound a thinker as Dr. Weissmann. 



2. There is one point, however, in Dr. Weissmann's paper, to 

 which I would take some slight e,\ception. He says, " There is no 

 essential, but only individual differences between the nuclear sub- 

 stance of the spermatozoon and of the ovum. There are no such 

 things as male and female nucleaj- substances, but only male and 

 female cells, carriers of immortal germ plasm." Now, if by ' essen- 

 tial differences' he means mysterious or occult differences, such as 

 are usually attributed to sex, he is probably right ; but surely sexual 

 reproduction is a device of nature whereby greater individual dif- 

 ferences of nuclear substances are produced than could have been 

 gotten in any other way. Such extreme individual differences are 

 called ' sexual ' in the case of organisms : why not also in the case 

 of nuclear substances ? 



3. In the other paper referred to, Hatschek, after criticising the 

 views of Weissmann and others, goes on to give his own theoretical 

 opinion; viz., " that in sexual reproduction we must recognize a 

 remedy against the action of itijurious variability." He then goes 

 on to show that disease or injurious variation of any kind in an in- 

 dividual would be indefinitely continued by non-sexual modes of 

 reproduction, but in sexual reproduction is quickly eliminated by 

 crossing with other strong and healthy individuals. Now, precisely 

 this view is very distinctly brought out in my article on genesis of 

 sex. Referring to the reasons for the introduction of sexual repro- 

 duction, I say (p. 177), " The reason is probably this : Among all 

 the qualities, good and bad, strong and weak, inherited {by the off- 

 spring) from both sides, there is a sort of struggle for life, and a 

 survival of the best and strottg est qualities." The same thought 

 is expressed in many ways in my book on evolution, already re- 

 ferred to. Joseph LeConte. 



Berkeley, Cal., April 24. 



Catching Fixed Forms of Animal Life on Transparent Media 

 for Study. 



In studying forms of animal life that become fixed to foreign 

 bodies during their early stages of development, it is an obvious 

 advantage to the investigator if they can be induced to attach 

 themselves to transparent media, such as glass or mica, so that 

 they may be studied without disturbance under the microscope 

 with transmitted light. 



Several attempts have been made to secure young oysters on 

 glass by Prof. John A. Ryder," Dr. R. Horst,'' and Lieut. Francis 

 C. Winslow,'' but with only very partial success. Professor Ryder 

 once found larvse attached to the glass sides of an apparatus in 

 which artificial propagation was being carried on. Dr. R. Horst 

 tried ground and plain glass, but secured only two on the latter. 

 Prof. Karl Mobius, in the Zoologischer Anzeiger of Jan. 22, 1883, 

 ■describes a successful attempt to catch fixed organisms on glass. 

 He used microscope-slides, and secured annelids, hydroids, polyps, 

 Bryosoa, Infusoria, diatoms, etc. Prof. B. H. Van Vleck informs 

 me that he habitually secures fixed forms of low organisms on glass 

 microscope-slides tor study. 



During the summer of 1887, I was studying the development of 

 the oyster (0. virginiana Lister) at Buzzard's Bay ; and as I was 

 anxious, if possible, to get them growing on glass, I tried several 

 methods to accomplish the desired end. During my work I had 

 very valuable assistance and suggestions from Dr. E. B. Larchar 

 of Onset, whose disinterested aid I here acknowledge. 



In a small pond-like estuary, bare at low tide, on the 14th of 

 July, I stretched wire netting between stakes driven into the sand 

 and raised about a foot from the sand. On this were laid panes of 

 glass, fastened in place with clothespins. Other panes were sus- 

 p ended from the sides, some in the plane of motion of the incom- 

 ing tide, others opposed to it. Lamp-chimneys were also suspended 

 from the apparatus. I used some fifty panes and twelve chimneys, 



I J. A. Ryder, On the Mode of Fixation of the Fry of the Oyster (Bull. U.S. Fish 

 Com., ii. 1882) ; An Account of Experiments in Oyster-Culture, and Observations 

 relating Thereto (Rep. U.S. Fish Com., 1882), Washington, 1884. 



= R. Horst, On the Development of the Oyster, O. cdiilis L. (Rep. U.S. Fish Com., 

 1884), Washington, 1886. 



3 F. C. Winslow, Notes upon Oyster Experiments in 1883 (Bull. U.S. Fish Com., 



but met with almost total failure, securing only two oysters, one of 

 which, however, grew to twenty-one millimetres in diameter. A 

 few barnacles became attached to the glass. 



One of the most successful spatting-grounds for oysters at Buz- 

 zard's Bay is a sand-spit exposed about four hours at low water. 

 Here the incoming tide divides, one branch flowing to Onset, and 

 the other to Buttermilk Bay. The force of the current is very 

 great. On this bar, at the suggestion of Dr. Larchar, earthenware 

 drain-pipes were partially sunk in an upright position, and loosely 

 filled with broken glass. Six- inch and four-inch pipes were used, 

 and at different elevations above the sand. I did not secure any 

 spat in the four-inch pipes. A six-inch pipe sunk nearly to the 

 level of the bar was successful, but in an unlucky day was filled up 

 with sand, and the young oysters buried. Six-inch pipes, reaching 

 about ten inches above the bar, were the most successful, and on 

 the glass in them I got large numbers of young oysters. Suitable 

 conditions for the success of the undertaking were therefore as 

 follows : (i) a strong tide-way, which would bring plenty of free- 

 swimming fry, and afterwards abundant food for their mainte- 

 nance ; (2) an area of quiet water within the pipe, in which the fry 

 could settle and attach themselves to the smooth glass ; (3) the 

 absolute shutting-out of violent currents which would detach them 

 from their precarious abiding-places. 



I first found spat on the glass on the 25th of July, and on the 

 28th took out a pane 6 by 4| inches square, on which I have just 

 counted eighty-two young oysters, as it is still in my possession in- 

 tact. This was only exceptional in the size of the glass, as other 

 pieces bore nearly or quite as many spat proportionally to their 

 area. Spat were secured in the pipes until the 29th of October, 

 when few were left, large numbers having dropped off by the 

 natural dissolving action of sea-water upon the organic cement 

 by which they are attached. 



Besides oysters, Anomias, Crepidulas, and Bryozoa freely at- 

 tached themselves to the glass, presenting admirable opportunities 

 for studying them alive and undisturbed. 



The nature of my researches required that I should get young 

 oysters with shells as clean and perfectly preserved as possible. 

 In May, year-old oysters were found very beautifully preserved on 

 the inside whorls of a dead Busycon shell, where they were com- 

 pletely protected from all eroding action, and clean. To imitate 

 these conditions, in the salt-pond above referred to, I suspended a 

 large number of two-and-a-half and three inch flower-pots in- 

 verted, from galvanized wire stretched between stakes driven firmly 

 into the sand. The pots were raised about six inches from the 

 sand. They met with entire success. The pots in many instances 

 were literally almost covered with spat. On the outside of the 

 pots very little, and on the inside no, sediment was deposited, as 

 the pots hung like suspended bell-jars, so that the oysters were 

 perfectly clean and very finely preserved. Further, on account of 

 the porosity of the earthenware, the oysters had less hold than on 

 natural cultch of stones and shells, and were easily removed for 

 study. Robert T. Jackson. 



Cambridge, Mass., May 4. 



Answers. 



31. Blonde .\ND Brunette. — A week or two ago a corre- 

 spondent of yours complained of the lack of precision of meaning 

 attached to the terms ' blonde ' and ' brunette,' and the want also 

 of words treating of intermediate shades of color as applied to the 

 hair and complexion of Caucasian human beings. There is cer- 

 tainly a need of more convention on this point ; for it seems strange 

 that lower animals, and even inanimate objects (%'ide dry-goods, 

 etc.), should be minutely characterized as regards color, whilst their 

 lords or makers are not. It would seem as if a century and a half 

 ago there was such better understanding about terms of color as 

 this gentleman wishes to see established. In the Spectator one 

 meets with proof of this. In one place I remember a lady (assumed) 

 writer draws the distinction between herself and a friend in the 

 matter of complexion as between an olive and a brunette ; and the 

 term 'a handsome black man ' (to imply the latter hue in a man) 

 is also met with in the writings of the last century. 



Alfred J. Hill. 



St. Paul, Minn., May 3. 



