262 PROCEEDINGS OF SOCIETIES. ['j°oumii,May1'l«7a' 



one animal was seen occupying the case of the other; drawings of 

 this 8uj)posed sexual process was exhibited to the Society, and Mr. 

 Hogg suggested the value of a systematic and careful examination of 

 these animals throughout the year, and during their various stages of 

 development, which might possibly show many departures from the 

 common type. 



Mr. Slack then read a paper by Mr. H. C Sorby " On Colouring 

 Matter derived from the Decomposition of Minute Organisms." 



The President said that Mr. Sorby had sent him two letters last 

 year on the subject of his present paper, and had promised a fuller 

 account of his experiments in a future communication to the Society. 

 This interesting communication had just been read. The specimens 

 of the dichroic fluid forwarded some little time ago by Mr. Shej^j^ard 

 gave two essentially diiferent spectra dependent on the presence or 

 absence of albumen, and hence Mr. Sorby was led to conclude that the 

 first dichroic fluid, which had given the same remarkable spectrum both 

 to Mr. Browning and himself, was in point of fact a mixture of the 

 albuminous and non-albuminous fluids. He (the President) had been 

 able to report that such was the case. It would be in the recollection 

 of the Fellows tliat Mr. Shcppard had given us an account of his own 

 early experiments, and that Sir. Eay Lankester had made some rather 

 stringent criticisms upon it, inasmuch as he had stated that Mr. 

 Sheppard had gone out of his way to conjure up a mystery quite un- 

 necessarily. Now, though he (the President) had a great respect for 

 Mr. Eay Lankester's zeal, and valued the results of his microscoincal 

 investigations, he could not but think that in this instance his zeal had 

 been allowed to outrun his discretion. It did really appear, as was 

 acknowledged by Dr. Cohn in a letter to Mr. Sheppard, that Mr. Shep- 

 pard had produced a new dichroic fluid, new to English microscopists, 

 and new to Mr. Sorby. The natural colour, which has a spectrum of 

 its own, was probably due to the small amount of albumen naturally 

 present in the confervoid mass, but Mr. Sheppard's artificial addition 

 of albumen produced a new fluid characterized by a new spectrum ; 

 and Mr. Sorby, speaking of the chemical effects of reagents on this 

 colour-, says in his note of June 12, 1869, "Neither ammonia, citric 

 acid, or sulphate of soda produce any change. It is a colour entirely 

 new to me." The President observed, in conclusion, that the whole 

 series of experiments was very interesting, as showing the accm-acy 

 of spectroscopic work and the dej)endcnce to be placed on fii-st-rate 

 observers. 



Mr. T. Charters White said that about a fortnight ago a friend of 

 his had brought up a bottle of dichroic fluid, which he had collected at 

 St. Leonard's and sent to Mr. Sorby for his inspection, and he affirms 

 that it is identical under spectroscopic examination with that found by 

 Mr. Sheppard. It was observed in a stream in which there was a con- 

 siderable ferruginous deposit. With reference to the changes of colour 

 produced by the presence of albumen, he would remark that a very 

 peculiar action takes place between vegetable substances and albumen, 

 and it was a point to which he should like to see Mr. Sorby 's attention 

 directed. 



