. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. Fig. 2. Tubulanus nothus, Burger. A, transverse section of head at anterior end of mouth; B, transverse section of body at nephridial canal. narrow lumen and lies above the rhynchodaeum. Where the pharyngeal nerves leave the brain the lateral blood spaces are joined beneath the rhynchodaeum by a ventral connecting lacuna and at the same place the laterals are again united with the median dorsal. The latter shortly afterwards disappears. Immediately behind the ventral connecting blood space a pai
. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. Fig. 2. Tubulanus nothus, Burger. A, transverse section of head at anterior end of mouth; B, transverse section of body at nephridial canal. narrow lumen and lies above the rhynchodaeum. Where the pharyngeal nerves leave the brain the lateral blood spaces are joined beneath the rhynchodaeum by a ventral connecting lacuna and at the same place the laterals are again united with the median dorsal. The latter shortly afterwards disappears. Immediately behind the ventral connecting blood space a pair of small vessels separate off" from the laterals. These remain close to the angle of the pharynx, but at the posterior end of the mouth they rejoin the laterals. There are subsequently one or two downward extensions of the laterals forming small loops (Fig. 3). I could not trace the close connection of the vascular system with the excretory tubules described by Oudemans (1885) in Carinella annulata. The excretory tubules occur above the lateral vessels and open to the ex- terior by a single duct high up on the dorsal surface (Fig. 2B). The nervous system lies between the basement membrane and the circular muscles. The brain consists of two lateral curved plates of tissue with no observed demarcation be- tween cellular and fibrous tracts. The plates are united by grapbhic reconstruction showin a stout ventral commissure, and a little farther back by a the vascular system (dorsal). slender dorsal commissure. There is little differentiation into dorsal and ventral ganglia until the posterior end of the brain. Anteriorly the brain breaks up into many nerves to serve the tip of the head. Just in advance of the ventral commissure a pair of nerves is given off for the proboscis. Another pair originates from the ventral ganglia after the commissure and innervates the pharynx. A mid-dorsal nerve intersects the dorsal commissure. It passes down the body between the basement mem-.
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Keywords: ., bookcentury1900, booksubjectocean, booksubjectscientificexpediti
