48 



that had been taken in a free state, or had been pulled out of an ovisac. All this put 

 together gives the result, that I have been able to examine the larvae of twenty-three species, 

 lacking only the larva of Stenothocheres Sarsii and nineteen species of Splueronella ; thus I 

 possess the larva of Sten. egregius, of fifteen species of Sphceronetta and of all seven species 

 of the four remaining genera. Fortunately the fifteen species of Spkceronella represent nearly 

 all the more important types of this large genus. 



As for the illustrations, I beg to notice that I have frequently omitted the two pairs 

 of natatory legs, or at least their branches, as their representation, as a rule, would have 

 been exceedingly difficult, and the omission is of little consequence, as the number and the 

 arrangement of the natatory hairs are very much alike in the different species. In some 

 cases the abdomen is also left out. My representations of the maxillulae include all that a 

 careful study enabled me to observe; however, I am inclined to think that a better material 

 would sometimes have allowed me to discover one — occasionally two — more branches. 



II. Structure of the Larvce. The length of the body usually varies between '20 and 

 •25 mm. ; the longest larva I found belonged to Splicer, decorata, and it is '30 mm. long, the 

 shortest, - 15 mm. in length, belongs to Eomoeoscelis minuta. The body is divided into two 

 parts: the cephalo thorax and the abdomen. The cephalothorax is somewhat depressed, 

 usually oval and about IV2 time as long as it is broad, sometimes (Mysichon, pi. XII, fig. 2h) 

 more elongated , almost double as long' as it is broad ; it consists of two divisions, namely, 

 the cephalothorax properly speaking, and a single trunk-segment (pi. Ill, fig. 3 k), which are 

 joined by a rather sinuate articulation, whereas the trunk-segment is between five and eight 

 times (in a single case about eleven or twelve times) shorter than the anterior division. 

 I have found behind the segment mentioned a very short portion which looked like the 

 rudiment of a second free segment (pi. Ill, fig. 3k) and belonged to the cephalothorax, not 

 to the abdomen; I cannot, however, say anything definite about this part and will content 

 myself with stating what I have observed. The abdomen is narrow, and its length varies 

 between a little more than one sixth and rather more than one third of that of the cephalo- 

 thorax ; it always consists of three distinctly separated segments and has two caudal stylets, 

 winch as a rule are plainly articulated on the third segment, but sometimes are coalescent 

 with it (e. g. pi. I, fig. 1 1). 



The foremost half of the large anterior division of the cephalothorax is always 

 provided with antennulse, antennae, rostrum with mandibles, maxillulae, maxillae and maxillipeds ; 

 the hindmost half has a longer or shorter odd pouch, which turns backward, decreasing in 

 width towards its distal end (pi. I. fig. 11, 1) ; its posterior part forms a free, either pointed 

 or rounded bag along the ventral surface, often covering the transversal band which unites 

 the first pair of natatory legs (pi. Ill, fig. 31), sometimes even the band between the second 

 pair of natatory legs (pi. II, fig. 11). The first pair of natatory legs is situated at the 

 posterior extremity of the first division of the cephalothorax, whereas the second pair 

 proceeds from the free trunk-segment. It may be mentioned finally, that Salensky has 



