GOBIOIDS. 



241 



The membrane tliat unites the two ventinl fins, may 

 soraetiines be wanting in front; ;uid Win iiier" attempted 

 to make the presence or absence oi' this membrane a 

 generic character. But as it may be wanting in spe- 

 cimens of these species'' perfectly typical in other re- 

 spects, we ciin regard this only as an individual de- 

 parture from the normal structui'e of the genus. 



One of the most remarkable ])eculiarities of this 

 subfamily is the structure of the system of the lateral 

 line. The system is not without the so-called muci- 

 ferous ducts". In Gobiii.i nir/cr for example, these ducts 

 with their pores appeal- on the head, both in tlie hind 

 margin of tlie preoperculum, on the parietal sides and 

 the forehead (in a line from the upper corner of the 

 branchial opening to the middle of the hind margin of 

 the eye), between the eyes and on the snout, on the 

 inner side of the nostrils. Solger'', however, searched 

 in vain for sensory organs in these ducts. On the 

 other hand, the cheeks, the branches of the lower jaw, 

 the gill-cover, the occiput, and one row of scales on 

 the sides of the body or, at least, some of the scales 

 in that row which corresponds to the lateral line, are 

 furnished with external, small papilhe, which have the 

 appearance of sensory organs, and are arranged in more 

 or less regular roAvs. The histological structure of 

 these sensoi'y oi-gans, composed, as they are, partly of 

 inditterent, epithelial cells and partly of pear-shaped, 

 sensory cells, tipped with bristles, which project into 

 the cupula covering the top of thi- organs and tilling 

 a cavity bare of epidermic cells, corresponds to the 

 structure ascribed by F. E. Schultze" to the sensory 

 organs of the lateral line proper and the other parts 

 of this system. The position of these organs, which lie 

 uncovered on the surface of the skin, represents the 

 earlier developmental stages of the system of the lateral 

 line, as Schultze has shown, before it is furnished 

 with ducts, originally channelled, and at length perfected 

 by the coalescence of the dermal folds which liave risen 

 on each side of the sensory organs ali-eady present. 



Similar free, "embryonal", lateral organs also occur in 

 the fry of the Pike and the Sticklebacks', and may 

 perhaps l)e present in many other fishes, especially those 

 in which the lateral line is indistinct or broken; but 

 nowhere are they so distinct as in some members of 

 the subfamily Gobiince. 



The generative organs of these fishes call for spe- 

 cial attention. In the male of the Common Scandina- 

 vian Goby {Gohius nUjer), during the spawning-season, 

 the testes are considei'ably expanded posteriorly, lobate 



Fig. 63. Deriiial papilla? on the head (raagn. 1' 2 fliaiii.) and on two 

 of the scales of the left lateral line (niagn. 6 diam.) in Gobius nigev. 



After WiNTHER. 



and of a spongeous structure with relatively large 

 meshes. The two hindmost lobes, one on each testis, 

 or sometimes three — one of them in this case being 

 unpaired, and issuing from the union of the rasa defe- 

 rential or belonging to the left testis — issue from 

 the testes proper in the form of flat, triangular disks 

 Avith rounded corners, which are considerably broader 

 and even thicker than the latter, but like them open 

 into the rasa deferentia. Rathke described them* 

 under the name of auxiliary generative organs, and ex- 

 plained their function partly as prostatic formations, 



" Naturh. Tidskr. Kblivn, ser. 3, vol. XI, p. 40. 



* In a Gobius pictus (Auctt.) from Allinge (Boniholiii) the nK-iiibranc whicli in other eases unites the ventral fins, is so small and 

 thin, that it was only after the minutest examination tliat we could find any traces of it. 



" Cf. Cdv., Vai.., Hist. Nat. Poiss., vol. XII, pp. 33 and 87: Winther, X.iturh. Tidskr. Kblun, ser. .3, vol. IX, p. ISl. plate VII. 



•' Arch. Mikr. Anat., Bd. XVIII (1880). p. 377. 



' Arch. Mikr. Anat, Bd. VI (1870), pp. (52 etc., jilates IV— VI. 



'■ LEvmo, Xeue Beitr. Anat. Keuntn. d. llautdecke nnd Ha'it.iiniiesort/aiic der Fische. Festschr. z. Feier d. Hundertj. Best. d. Naturf. 

 Gesellsch. in Halle " S, 1879. See also Solger, 1. c. 



'J According to Rathke. 



'' Uber den Dannkanal und die Zeagungsorgnne der Fische, p. 201, tab. V, fig. 9-11, in Beitr. 7.. Gescb. d. Thierwelt, Abth. 2 

 (Schr. Xaturf. Ges. Danzig, Heft. Ill, 1824). Cf. also Kroyer, Danm. Fiske, vol. I, p. 395. 



Scandinavian Fishes. 



31 



