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 Sphrrronella; thus I 

 possess the larva of Sten. egregins, of fifteen species of SplueroneUa and of all seven species 

 of the four remaining genei-a. Fortunately the fifteen species oi Spheeronella 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 consetiuence, 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 maxillulaj 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. Sfrtichire of the Larree. The length of the body usually varies between 20 and 

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

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

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

 usually oval and about IV2 time as long as it is broad, sometimes (J!f«/«V7?ow, 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, 

 which as a rule are plainly articulated on the tliird 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 antennulae, antennae, rostrum with mandibles, maxillulse, maxillae and maxillipeds ; 

 the liindmost 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. 3 1), 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 Saleusky has 



