192 



CHAETOGNATHA 



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

 the coast line. S. serratodentata, Mediterranean. S. enflata, 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 Loth 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 

 FIG. 105. Spadella draco. Dorsal view, even farther. Two rows of spines 



x 12. (From Hertwig.) a, Cephalic 0.111 o n i 



ganglion ; b, commissure between the on the head. Small animals, not 



cephalic ganglion and the ventral ; c. longer than 1 Clll 

 eye ; d, olfactory organ ; e, aliment- . 



ary canal ; /, ovary ; g, oviduct (the *->. CepflOlOptera r>USCll IS tlie 



line goes a little beyond the duct) ; h, sma ll es t species of Chaetognatha, 

 testis ; j, vesicula semmahs. 



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. batziana Giard, and S. gallica 

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

 their description is too indefinite to permit of accurate character- 



