192 



CHAETOGNATHA 



CHAP. 



cm. in length, widely distributed, and as a rule living near 

 the coast line. S. serratodentata, Mediterranean. S. e?iflata, on 

 the surface of the sea, Mediterranean and Madeiran. S. minima 

 a very small species, 1 cm. in length, Mediterranean. S. falcidens, 

 Atlantic, off the coast of New Jersey. 



(ii.) Krohnia Langerhans. A single lateral fin extending on 



to both trunk and tail segment, 

 no lateral epidermal extensions 

 behind the head, only one row of 

 spines on the head. Trunk longer 

 than the tail. 



Krohnia has but two species : 

 K. hamata Mobius, with a length 

 of 3-4 cm., found in the North 

 Atlantic and at considerable 

 depths, 200 to 300 fathoms; 

 and K subtilis Grassi, 1*5 cm. 

 long, with an extraordinary slender 

 body and a relatively large head, 

 found at Messina, but very rare ; 

 as a rule only one specimen has 

 been found at a time. 



(iii.) Spadella Langerhans. 

 A single pair of lateral fins ; these 

 are situated on the tail segment. 

 Behind the head a thickening of 

 the epidermis extends down each 

 side of the body to the fin, or 

 even farther. Two rows of spines 

 on the head. Small animals, not 

 longer than 1 cm. 



S. cephaloptera Busch is the 

 smallest species of Chaetognatha, 

 attaining at most a length of *5 

 cm. The body is not so transparent as in other species, and is of 

 a yellowish colour. It has been found from the Orkney Islands 

 to the Mediterranean. Strodtmann is of the opinion that the 

 three species S. mariana Lewes, S. hatziana Giard, and S. gallic a 

 Pagenstecher differ from the above-named only in size, or that 

 their description is too indefinite to permit of accurate character- 



*Fig. 105. Spadella draco. Dorsal view, 

 x 12. (From Hertwig.) a, Cephalic 

 ganglion ; b, commissure between the 

 cephalic ganglion and the ventral ; c, 

 eye ; d, olfactory organ ; e, aliment- 

 ary canal ; /, ovary ; g, oviduct (the 

 line goes a little beyond the duct) ; h y 

 testis ; J, vesicula seminalis. 



