1905.] Effects of Alkalies, etc., on Eggs of Echinus. 



109 



tively by titration the reaction to both phenol-phthalein and " di-methyl " at 

 the end of each experiment after growth had stopped. It was found that 

 even where alkali had been added at the commencement of the experiment 

 the reaction to phenol-phthalein had become slightly acid at the end in most 

 experiments. Since the amount of alkalinity to " di-methyl " had not altered 

 throughout the experiment, but gave in all cases very approximately the 

 alkalinity of sea-water plus or minus the alkali or acid artificially added, it 

 follows that the change in reaction to phenol-phthalein must be due to a 

 very weak acid given off during the development of the embryos. Since 

 carbon-dioxide produces exactly the same effects, and respiration must occur 

 in the process of development, it is almost certain that the change in 

 reaction must be due to production of carbonic acid. On account of this 

 natural production of carbonic acid, the results of the first twenty-four 

 hours' growth are the most valuable, because here the alkaline reaction to 

 phenol-phthalein persisted, and the production of carbonic acid was small. 



After preliminary experiments had determined the range at which the 

 developing embryos were definitely affected by the different chemicals, a few 

 final experiments were made in which only two or three concentrations of 

 each chemical were included lying at about the proper range, and the last 

 such experiment was interrupted when the more advanced sets of embryos 

 had reached the morula or early blastula stage.* The embryos were fixed in 

 Flemming's and Hermann's fluids, embedded and cut in paraffin, and stained 

 for nuclear division by Heidenhain's iron-alum and haematoxylin staining, 

 following Flemming's description. The drawings illustrating the paper were 

 made from this series of preparations, with the exception of fig. 18, which 

 was drawn from the fresh growing cells. 



Reaction of Sea- Water of Port Erin Bay. — One hundred cubic centimetres 

 of sea-water was taken and titrated against decinormal caustic soda solution, 

 (a) with di- methyl- amido- azo- benzol as indicator, and (b) with phenol- 

 phthalein as indicator. With the " di-methyl " in a first trial 2 - 35 c.c. were 

 required, in a second 2*37, therefore the alkalinity was = - 00236 normal. 

 With the phenol-phthalein - 24 c.c. and 0'22 c.c. were required, alkalinity 

 = 0-00023 normal. 



* After cutting sections, it was found that many of the cells described in Table XI 

 (pp. 123, 124) in the fresh condition as ruorulse really possessed in section a small central 

 cavity, and so are termed blastulse in the descriptions of the drawings. The organisms 

 described as blastulse in the tables showed in the fresh condition an outer layer of cells. 



