482 



NATURE 



[September 17, 1891 



not to belong to the pilchard ; Pouchet believed that the 

 pilchard's ovum is not pelagic. The identification of the 

 ovum was shown to be correct by further observations carried 

 out in the Laboratory with the ova obtained from the mature 

 fish. Similar results have been obtained by Marion, of Mar- 

 seilles. 



Another paper, by the same, dealt with the growth of food- 

 fishes, and their distribution at different ages, 



(1) Rate of Growth and Age of Sexual Maturity. — Numerous 

 specimens of the flounder {PI. flesus) were reared from the larval 

 state in the aquarium of the Plymouth Laboratory. Measured 

 in April, when a year old, they varied from 4 to 19 cm. (about 

 \\ to 7i inches). Specimens obtained in the Cattewater, and 

 known to be not less than a year old, are from 12 to 19 cm. in 

 length. None of these captive flounders, nor any taken in the 

 Cattewater, were sexually mature, but, according to Dr. Fulton, 

 of the Scottish Fishery Board, sexually mature flounders have 

 been observed which were only 7 inches long. It was con- 

 cluded, therefore, that {a) the rate of growth varies greatly for 

 different individuals, but its maximum for the first year is 19 cm., 

 or 7^ inches ; {b) sexual maturity is not reached till the end of 

 the second year, although the minimum size of sexually mature 

 individuals may be slightly exceeded by some specimens in one 

 year's growth. 



Similar results were obtained for the plaice {PI. platessa) and 

 the dab {PI. limanda). 



(2) Distribution. — The young of the above-mentioned species 

 in their first year, and of certain round fish, especially Gadus 

 luscus and G. minutus, occur in shallow water, within the 10- 

 fathom line. But there has hitherto been considerable difficulty 

 in obtaining young specimens of other more valuable species in 

 order to study their rate of growth. These species — namely, the 

 sole, turbot, brill, lemon sole, megrim {Aruoglossus tnegastoma), 

 do not pass the' first year of their lives in shallow water. Young 

 soles in the larval state occur in tidal pools at Mevagissey, and 

 young turbot and brill 2 to 3 cm. in length are commonly found 

 from June to August in Plymouth Sound and Sutton Pool, 

 swimming at the surface in a semi-metamorphosed stage. 

 Soles a little over 16 cm. in length are frequently taken 

 in Plymouth Sound in summer ; these are just over one 

 year old, and are not sexually mature. Turbot 23 to 34 cm. 

 long may be taken in 5 to 7 fathoms ; these also are over 

 one year old and not sexually mature. But the young stages 

 between 3 months and 12 months old have not been taken in 

 shallow water, and apparently live at depths greater than 10 

 fathoms. It seems that our commoner and more valuable food- 

 fishes do not attain to sexual maturity till the end of their second 

 year, that their size at this age is subject to great individual 

 variation, and that the young in the first year of growth have a 

 characteristic distribution. Investigation of the deeper water 

 from this point of view is now being carried on at Plymouth. 



The distribution of Crystallogobius Nilssoni was recorded by 

 the same author. It had been found by Collett in the 

 Christiania Fjord and in other parts of Norway ; also at 

 Bohuslan, in Sweden. Mr. Cunningham dredged 100 speci- 

 mens at a single haul close to the Eddystone, in 27 fathoms of 

 water. Day mentions only one specimen found in British 

 waters — one taken by Thomas Edwards in a rock pool at Banff. 

 Mr. Holt subsequently dredged a number in 30 fathoms in 

 Ballinskelligs Bay. The species is probably fairly abundant 

 between 20 and 30 fathoms on smooth sandy ground all along 

 the British and Irish coasts. 



Mr. Cunningham also read a paper upon the larvae of the sea 

 crayfish {Palinurus vulgaris), describing most of the stages, and 

 particularly remarking upon the presence of the first maxilli- 

 pede in the newly hatched larva, which had been stated by 

 Richter to be absent. 



Prof. Herdman and Mr. J. A. Clubb communicated a paper 

 upon the innervation of the epipodial processes of some Nudi- 

 branchiate Mollusca. The cerata of the Nudibranchs were 

 regarded by Prof. Herdman as being probably epipodial out- 

 growths. 



The question has, however, been raised lately by Pelseneer 

 and others as to whether the so called epipodia of Mollusca are 

 all homologous structures, and one of the subjects of controversy 

 now is the origin of the nerve supply in various forms, it being 

 supposed that where the processes are innervated from the 

 pleural ganglia they are pallial in their nature, and where 

 supplied from the pedal ganglia they are to be regarded as 

 outgrowths from the foot. 



NO. I 142, VOL. 44] 



Consequently it seemed of importance to determine afresh 

 the origin of the nerves supplying the cerata in several different 

 types of Nudibranchiata, especially as the results of former in- 

 vestigations, depending entirely, we believe, upon minute dis- 

 section, are puzzling, and to some extent contradictory. We 

 have traced the nerves from the ganglia, by means of serial sec- 

 tions, in representatives of the genera Polycera, Ancula, 

 Tritonia, Dendronotus, and Eolis, with the following results : — 



In Polycera quadrilineata the cerebral and pleural ganglia 

 are completely fused to form a cerebro- pleural mass. The 

 "epipodial" nerves are found arising from the venti-al and 

 posterior part of this mass {i.e. distinctly from the pleural 

 ganglia), and they run along the sides of the back to supply the 

 ceratal ridges. 



In Ancula cristata the pleural ganglia are fairly distinct from 

 the cerebral. In a specimen cut into about 500 sections we find 

 in the looth section or so from the anterior end six distinct 

 ganglia (the cerebral, pleural, and pedal pairs) surrounding the 

 oesophagus. A few sections further back, the cerebrals disap- 

 pear, and then the epipodial nerves are found arising from the 

 dorsal edge of the pleural ganglia. The nerves soon turn 

 posteriorly, and then give off their first branches dorsally. 

 These branches enter the mesoderm of the body wall, and can 

 then be traced back through over a hundred sections to the first 

 pair of cerata, which they enter. The main nerve passes back 

 to the remaining cerata. 



In Tritonia and Dendronotus also the epipodial nerves arise 

 from the pleural ganglia ; but in Eolis (or Facelind) coronata we 

 find that the main nerves to the cerata arise distinctly from the 

 pedal ganglia. We have also traced in the same series of sec- 

 tions the ordinary pedal nerves to the foot proper ; so there can 

 be no question as to the nature of the ganglia from which the 

 nerves arise. The epipodial nerves spring from about the 

 middle of the pedal ganglion, rather on the dorsal surface, and, 

 after a short course, pass through the muscular layer of the body 

 wall and are distributed to the clumps of cerata. 



But, in addition to these main epipodial nerves in Eolis, we 

 find also a nerve arising from the compound ganglionic mass, 

 immediately ventral to the eye (probably, therefore, from the 

 pleural element), which goes to the front cerata. This pleural 

 nerve has its origin distinctly anterior to the origin of the main 

 epipodial nerves from the pedal ganglia. 



We arrive, then, at the curious result that the innervation ot 

 the ceratal processes is not the same in all these Nudibranchs. 

 In Polycera, Ancula, Tritonia, and Dendronotus, the epipodial 

 nerves arise from pleural ganglia, or from the ventral and pos- 

 terior parts of cerebro-pleural masses ; while in Eolis the chief 

 epipodial nerves are from the pedal ganglia, but there are also 

 smaller nerves from the pleurals. In the ordinary Rhipido- 

 glossate Gastropod, such as Trochus, the epipodial ridges and 

 processes are supplied, according to Pelseneer, by nerves arising 

 from the dorsal part of the elongated pedal ganglia. So, judg- 

 ing from the nerve supply alone, it might be said that the cerata 

 of Eolis are pedal in their nature, and homologous with the epi- 

 podial processes of Troclms, while those of Ancula and the rest 

 are totally distinct structures of pallial origin. But these dorso- 

 lateral processes in the various Nudibranchs are so much alike 

 in their relations, and are connected by such series of gradations, 

 that it is difficult to believe that they are not all homologous ; 

 and the presence of the accessory epipodial nerve in Eolis 

 arising from the pleural ganglion suggests the possibility of 

 another explanation, viz. that these outgrowths, starting at first 

 as pedal structures innervated by nerves Irom the pedal ganglia, 

 may have acquired, possibly as the result of having moved 

 further up the sides of the body, a supplementary nerve 

 supply from the adjacent integumentary nerves arising from the 

 pleural ganglia, and this supplementary supply, while remaining 

 subordinary in Eolis, may in the other types have gradually 

 come to supplant the original epipodial nerves, which are now 

 no longer found in such forms as Polycera and Ancula. This is 

 at present only a suggestion, which may be disproved or sup- 

 ported by the examination of the nerves of a number of 

 ' additional Nudibranchs. 



Prof. W. N. Parker read a paper containing the results of 

 some experiments on respiration in the tadpoles of the common 

 frog. After referring to the great power of adaptation to ex- 

 ternal conditions seen amongst amphibious larvae, the author 

 described some experiments on frog tadpoles, which, although 

 not yet complete, show as follows : — (i) Soon after the lungs 

 become functional — i.e. in tadpoles measuring more than 2 cm. 



