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 larvee of twenty-three species, 
lacking only the larva of Stenothocheres Sarsii and nineteen species- of Spheronella; thus L 
possess the larva of Sten. egregius, of fifteen species of Spheronella and of all seven species 
of the four remaining genera. Fortunately the fifteen species of Spheronella 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 maxillule 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. 
IL. Structure of the Larve. The length of the body usually varies between -20 and 
°25mm.; the longest larva I found belonged to Spher. decorata, and it is ‘30mm. long, the 
shortest, 15 mm. in length, belongs to Homoeoscelis minuta. The body is divided into two 
parts: the cephalothorax and the abdomen. The cephalothorax is somewhat depressed, 
usually oval and about 11/2 time as long as it is broad, sometimes (DZysidion, pl. 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 (pl. III, fig. 3k), 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 (pl. III, 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 third segment, but sometimes are coalescent 
with it (e.g. pl. I, fig. 11). 
The foremost half of the large anterior division of the cephalothorax is always 
provided with antennule, antennze, rostrum with mandibles, maxillulee, maxillze and maxillipeds; 
the hindmost half has a longer or shorter odd pouch, which turns backward, decreasing in 
width towards its distal end (pl. 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 (pl. III, fig. 31), sometimes even the band between the second 
pair of natatory legs (pl. 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 
