406 M. E. Hesse on the Pranizae and Ancei. 



few days, he preserved alive in sea-water, instead of putting it 

 into spu'its. On his return, he found its place occupied by an 

 Anceus. From the difference of form, especially in the size 

 of the head, he thought that he must have fallen into some 

 error; but subsequent observations confirmed his first view of 

 the relations existing between the two forms. On the 20th of 

 July 1853 he found a Praniza on the fins of a Plaice {Platessa 

 vulgaris), which became an Anceits on the 5th of November. On 

 the 19th of August 1855, three Pranizce were found on the 

 body of a red Gurnard {Trigla Pini) ; these were transformed 

 into Ancei on the 1st of September. On the 21st of September 

 1856, several Pranizce were taken on a Gurnard (7*. Hirundo), and 

 became converted into Ancei on the 8th of October. On the 

 10th of June 1857, he found under stones, on a somewhat 

 muddy part of the shore, a great number of Praniza intermixed 

 with male and female Ancei. In a few days all the Praniza 

 underwent their metamorphosis, "so that nothing but Ancei 

 remained." And on the 29th of August 1857, he found 

 twenty-one Pranizce in the mouth of a Wrasse {Labrus Bergylta)^ 

 which all became transformed into Ancei on the 6th of September 

 and following days. 



In all cases, since this period, the Pranizce met with by the 

 author have undergone the transformation above described, and 

 the Ancei thus produced have copulated and produced fertile 

 ova, the first products of which were Pranizce. The cast skins 

 of the Pranizce were also found at the bottom of the vessels in 

 which they were preserved, and their examination has enabled 

 the author to elucidate the structure of the mouth in these 

 Crustacea. The facts observed by the author demonstrate that 

 the Crustacea hitherto described under the generic names of 

 Praniza and Anceus must now be regarded as forming one 

 genus, for which the latter name must be retained, as it is only 

 in the Anceus-iovm that they are capable of reproduction. 



Of the general characteristics of the Ancei M. Hesse speaks 

 in the following terms : — " Of all the Crustacea inhabiting our 

 coasts, there are certainly none more worthy of attracting the 

 attention of naturalists than the Pranizce, or rather the Ancei, 

 whether we consider the brilliancy and variety of their colora- 

 tion, the lightness and elegance of their forms, or the singularity 

 of their mode of life ; but, for the present, I shall confine myself 

 to speaking of the transformations which they undergo, from 

 their escape from the e^^ until they attain the perfect state. 

 "When these Crustacea, still in the Praniza-&tate, are superficially 

 examined, we are struck by the resemblance they present to some 

 insects of the order Coleoptera, especially of the family Carabidse; 

 but this analogy becomes still more striking when they have under- 



