mVERTEBKATA, CRYPTOQAMIA, MICROSCOPY, ETC. 427 



tomy, but adds something like a revision of the group, with several 

 new species. 



In the study of the Nervous System, which is much obscured by pig- 

 ment, staining with Bealc's carmine, after treatment with 2 per cent, 

 osmic acid, was found useful. In Protella the brain is three times the 

 size of one of the large thoracic ganglia. The " chief brain " consists 

 of two pear-shaped bodies, which form the apex of the whole by two 

 pointed processes, terminated by connective-tissue bands, which are 

 directed upwards and inwards. It is connected by broad, thin com- 

 missures with the other large ganglia, of which there are four pairs. 

 In front of its base, and connecting it with the other ganglia, lie those 

 which originate the ujjper antennary nerves, fi'om which the nerves pass 

 directly forwards ; below this pair are the inferior antennary ganglia, 

 of similar size and shape. The chief part of the base is formed by 

 two large subquadi-angular masses, the ganglia of the commissure, 

 which lie behind the last named. The commissiu'e proceeds from their 

 lower edges. On a kind of ledge on the upper surface rest the optic 

 ganglia, which are smaller rounded masses lying at the back of the 

 brain, connected only with the chief brain ; the eyes lie at their sides. 

 These details are much the same in Proto as in Caprella ceqailahra. 

 In this species the outline of the whole brain is that of a rude oblong, 

 with the long axis passing through the chief brain above and the inferior 

 antennary ganglion below. This is caused by the fusion of the upper 

 antennary with the commissural ganglion, forming a large joint mass 

 above the lower antennary ; the optic ganglia lie between this mass and 

 the chief brain. The sub-oesophageal ganglion and the first of the body 

 ganglia do not fuse together — as stated by Dohrn* and Gamrothf — in 

 Protella. The former sends small nerves to the beginning of the 

 alimentary canal and to the mouth organs ; the latter supplies the first 

 pair of feet, and perhaps also the alimentary canal. 



The posterior ganglia present some points of interest ; the penulti- 

 mate thoracic segment contains two, of which the first supplies the 

 penultimate, the second the last pair of legs by stout branches ; a 

 division of the nerve from the latter goes upwards to the intestine. 

 Behind the latter ganglion, and connected with it by two trunks, fol- 

 lows a pair of much smaller nervous masses, sending two twigs to the 

 abdomen, and between it and the posterior thoracic lie two more such, 

 connected with their anterior and posterior neiglibours, but, as is also 

 the case with the other two small ones, not with each other ; behind 

 them both lies an azygos mass which completes the plexus of five 

 small ganglia. Of these the anterior pair represents a lost abdominal 

 BCgmcnt ; the second pair belongs to. the last, and the unpaired mass 

 to the first abdominal segment. Of the lost segment itself a trace 

 seems to occur in Proto. 



In young individuals, taken from the brood-chamber of the female, 

 the brain presents a less differentiated condition than in the adult, the 

 distinction of the ganglia from the chief brain being indicated only by 

 grooves ; the second thoracic ganglion is larger, and the third and 



* ' Zcitsclir. wis.-. Zodl.,' xvi. p. 2i5, &c. 

 t Ibid., xxxi. p. 101, &c. 



2 F 2 



