ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 353 



The body-cavity or " uterus " is strongly developed. The number of 

 lateral branches from its median portion (over the intestine) does not 

 correspond to the number of intestinal branches, and the arrangement is 

 not symmetrical. It opens into the extreme end of the cloaca. The two 

 ovaries, lying one behind the other, and really unpaired, are situated 

 in the middle third of the body above the intestine. The much branched 

 testes are distributed over the ovaries and intestine. The anterior and 

 posterior branches of the vas deferens open on each side in the seminal 

 vesicle. The male genital openings lie between the third pairs of 

 parapodia and the corresponding lateral organs. There is a weakly 

 developed penis. 



The nervous system is ladder-like, with eight pairs of lateral nerves 

 and an unpaired posterior nerve. The pair of nerves farthest forward 

 form the oesophageal nerve-ring. The musculature is weakly developed. 

 There are several pairs of nephridia, and the number on the two sides is 

 not always the same. The animal is an endoparasite, and as such it 

 shows in comparison with other Myzostomida? a number of retrogressive 

 characters. 



Fedotov makes a careful comparison of the three genera — Myzosto- 

 mum, Protomyzostomum, and Stelechopus, and comes to the conclusion 

 that Protomyzostomum is nearer to Nereidomorph Polychasts than are 

 the others. It shows primitiveness in its ladder-like nervous system, in 

 the position of its lateral organs, in the several pairs of nephridia, in the 

 elongated stomach with numerous main branches, in the absence of 

 sharp localization of the ovaries, and in the terminal position of the oral 

 and cloacal openings. It shows secondary adaptations to endoparasitic 

 life in the absence of cilia on the somatic epithelium and the insinking 

 of that epithelium, in the great reduction of parapodia and musculature, 

 and in the Planarian-like shape. It is also distinctively marked by the 

 absence of marginal cirri, radial muscle-septa, and proboscis, and in the 

 very weak development of a penis. 



New Sagitta.* — Ellis L. Michael describes Sagitta calif omica sp. n., 

 and sets a good example by giving a table based on micrometer measure- 

 ments of fourteen structural features observed on a hundred of the best 

 specimens. The number of teeth and seizing jaws possessed by each 

 individual is recorded, and the state of maturity of the ovary and 

 seminal vesicle. The new form is readily recognized from all other 

 species by its massive and very long collarette, extending from the head 

 to the tail-septum, and thence to the seminal vesicles. 



In animals between 12 and 26 mm. in length, variation in the ratio 

 between the length of the animal and the length of the tail, the interval 

 from tail to ventral ganglion, the length and width of anterior fin, the 

 interval from anterior fin to ventral ganglion, and the length and width 

 of the posterior fin — is approximately constant, irrespective of the length 

 of the animal. Of all proportional measurements these are, therefore, 

 the safest for the identification of S. californica, and this is especially 

 true of the proportional length of the tail. 



* Univ. California!! Publications (Zool.) xi. (1913) pp. 89-126 (1 pi.). 



