GEPHYREA. 621 



ment in small clumps in the amoeboid cells of Echiurtts, and the spherical 

 corpuscles of Thalassema Nepttmi ; haemoglobin in the spherical corpuscles 

 of the last named, and in Hamingia arctica ; a pink or red pigment not 

 yielding any absorption-bands, but the colour of which is intensified by 

 contact with air or oxygen in the biconcave discs of Sipunculus mtdus ; it is 

 termed haemerythrin by Krukenberg. The pink pigment contained in 

 similar corpuscles in other species of Sipunculus, in some species of Phas- 

 colosoma, and of Bonellia minor, has not been investigated spectrosco- 

 pically *. The coelomic fluid of Sipunculus and Phascolosoma also contains 

 remarkable structures moving freely in it the ' Topfchen ' which are 

 shaped like a bell, with a ciliated mouth. They appear to be coelomic 

 cells detached from some portion of the alimentary canal, &c. The liquid in 

 the blood-vessels is corpusculated, and the corpuscles resemble those of the 

 coelome in Sipuncuhis midus and Echitirus. The ' Topfchen ' are said to 

 occur in it in the former (Brandt). In Thalassema Neptuni, however, it is 

 colourless, and does not contain ' corpuscles similar to those of the coelome' 

 (Lankester). 



With the exception of the Priapulidae all Gephyreans possess organs 

 known as genital or uterine pouches, segmental organs, or anterior ne- 

 phridia, which open outwards anteriorly on the ventral surface. The genus 

 Bonellia possesses but a single organ, as is sometimes the case in Hamingia 

 arctica ; so too Saccosoma, Epithetosoma, and tubicolous Sipunculidae 2 . 

 Other Sipunculidae, and H. arctica as a rule, possess a single pair, 

 Eckwrus two, the various species of Thalassema one, two, three, or four 

 pairs, one behind the other. The external apertures of these organs lie 

 one on either side of the ventral nerve-cord, and behind the ventral hooks 

 in Echiurids ; but when three pairs are present, the first usually opens in 

 front of and a little laterally to those structures (Lampert). The walls of the 

 organs are muscular, and except at the period of sexual activity, when they 

 are much distended with sperm or ova, they are small in size. Internal 

 openings into the coelome have not been found in all Sipunculids. In 

 others, and in Echiurids, they are present. In Sipunculidae they may be 



1 The brown pigment of Echiurus is probably identical with that occurring in other parts of the 

 body, e. g. in the walls of the anal caeca. The pink pigment of Sipunculus nudus tinges, according 

 to Ray Lankester, the sheath of the nerve-cord and a band underlying the alimentary canal. The 

 same authority states that in Th. Neptuni haemoglobin is present in the muscles of the middle region 

 of the body, in the thick coelomic epithelium covering the mesenterial bands of the alimentary canal 

 and of the anterior nephridia. Orange-red granules are plentiful in the same animal in the coelomic 

 epithelium of the vessels, of the sheath of the nerve-cord, of the median ventral line of the intestine, 

 of the four anterior nephridia, and the anal caeca. So too in Echiurus Pallasii. Sluiter states that 

 the alcohol in which a specimen of Th. erythrogrammon was preserved gave the spectrum of haematin, 

 indicating the existence of haemoglobin in the living animal. 



2 De Lacaze Duthiers found a pair of organs in a single specimen of B. viridis. See p. 74, 



A. Sc. N. (4), x. 1858. The single organ is usually that of the right side in B. viridis, of the left in 



B. minor. 



