798 RECORD OF CURRENT RESEARCHES RELATING TO 



myoblasts arc to be looked for in tlie epithelium of the coelom (body - 

 cavity). 



Poor as is the " cephalic cap " in muscles, it has a structure of 

 considerable interest, for it contains the nerve-trunks which connect 

 the ventral with the cephalic ganglion, as well as the eyes and the 

 optic nerves. In Spadella cephaloptera there was also to be observed 

 on either side a short tentacular process, which terminates in a knob- 

 like enlargement. 



After a short account of the enteric tract and the mesenteries, the 

 author passes to a consideration of the Generative Organs. In animals 

 which are sexually mature the hinder portion of the two cavities of 

 the trunk-segment may be seen to be almost completely filled with the 

 two ovaries ; these are more or less cylindrical bodies, which are only 

 attached by a thin and short mesentery ; they consist of a rather narrow 

 oviduct, and of a true ovary. The contents of the former vary in 

 individuals, and in some cases the author was able to detect in them 

 spermatozoa in active movement. There is some difficulty in under- 

 standing how the matured products escape to the exterior ; Hertwig is 

 of opinion that it is the hinder portion only of the oviducts which 

 serves for the extrusion of the eggs, while the large caecal portion 

 functions as a kind of receptaculum seminis. 



The male organs form, so far as the matrix of the spermatozoa is 

 concerned, a projection into the most anterior portion of the caudal 

 segment ; from this there are set free masses of unripe spermatozoa, 

 which may be seen to be executing a regularly circulatory movement. 

 The efferent ducts lie in the hinder portion of the caudal segment, 

 and the short canal has at its anterior end an infundibular ciliated 

 orifice. The spermatozoa are collected into a seminal vesicle, more 

 or less elongated and oval, but varying in form in the various species. 



The following table exhibits the system of the group : — 



Ch^tognatha. — Body consisting of three segments, separated by 

 septa, and provided with horizontal fins. The head with prehensile 

 hooks, spines, and a " cap," with two eyes, and an unpaired olfactory 

 organ ; coelom spacious. The enteron has two mesenteries, and ojieus 

 in front of the anenterous caudal segment. Four longitudinal muscular 

 bands. Nervous system consists of the ventral, the supra-oesophageal, 

 and the lateral cephalic ganglia. Trunk-segment with two ovaries ; 

 caudal segment with two testes. 



I. Sagitta. 



Unpaired caudal, two pairs of lateral fins. 

 (a) Species from 3-7 cm. long. 



1. S. hexaptera; 2. ;S. lyra ; 3. S. magna; 4. S. tricuspidata ; 

 5. S. bipunctata ; 6. S. serratodentata; 7. S. mariana ; 8. S. pontica ; 

 9. S. diptera ; 10. S. iriptera. 



II. Spadella. 

 Unpaired caudal fin ; one pair lateral fins. 

 1. S. cepTialoptera ; 2. S. draco ; 3. S. hamata. 



