The Genus Synchceta. By G. F. Rousselet. 275 



spring ; other kinds like S. littoralis, tavina, gyrina, vorax, cecilia, 

 and kitina like a little warmer weather, but are most erratic in 

 their sudden appearance and disappearance. S. grandis, stylata, 

 and longipes I have found only in the summer months, July to 

 September, whilst the pelagic marine species S. baltica, monopus, 

 triophthalma, and neapolitana seem to come to the surface in the 

 summer when the sea has been calm for a considerable time. 



All Synchsetse can be prepared easily and preserved fully 

 extended by the method I have described, of which the following 

 are the main stages : — Isolation in a watch-glass full of clean water ; 

 narcotisation with one or two drops of 2 p.c. cocaine or 1 p.c. 

 eucaine for about half an hour; killing and fixing with \ p.c. 

 osmic acid or Hermann's platino-osmic mixture, washing in water 

 (the marine species in sea water), preserving in 2£ p.c. formal- 

 dehyde. Marine species die fully extended when placed in dis- 

 tilled water. I possess preserved specimens of all the sixteen 

 species, and they are here under Microscopes for your inspection. 



I am very greatly indebted to my friend Mr. F. K. Dixon- 

 Nuttall, J.P., of St. Helens, for the excellent drawings of the various 

 species which accompany this paper, and which he has spared no 

 pains to make, with his accustomed skill, from the living animal 

 whenever possible, or from preserved specimens ; it would indeed 

 bave been impossible for me to have made such life-like represen- 

 tations, which so very greatly increase the value of this memoir, and 

 will assist in the identification of the various species. My thanks 

 are also due to Mr. John Hood, of Dundee, and Mr. H. E. Hurrell, 

 of Great Yarmouth, for sending me living specimens of the various 

 marine species, and to Dr. K. M. Levander, of Helsingfors, for 

 preserved specimens of the species living in the Baltic Sea, and for 

 the figures of S. monopus which he has been good enough to 

 send me. 



It has been found impracticable to draw all the animals on a uni- 

 form scale, as was at first intended, because if that had been done, 

 either the smaller Synchletae would have been drawn too small 

 for recognition, or else the larger species would have gone beyond 

 the limit of the plates. The figures therefore have been drawn 

 of convenient dimension, irrespective of their size, which must be 

 ascertained from the descriptions. All species vary considerably in 

 size, as the newly hatched individuals are only about half the bulk 

 *of the adult. In most cases the largest observed proportions have 

 been given. It must not be forgotten also, in comparing the figures 

 with the living animals, that the shapes also vary considerably, 

 some species being more conical when young, and stouter and 

 rounder occasionally when the food-material is exceptionally 

 abundant. 



It has not been the object of this paper to give an exhaustive 

 description of the minute anatomy of the various organs of 



